Online Etymology Dictionary

common law (n.): mid-14c., "the customary and unwritten laws of England as embodied in commentaries and old cases" (see common (adj.)), as opposed to statute law. Phrase common law marriage is attested from 1909.
common sense (n.): 14c., originally the power of uniting mentally the impressions conveyed by the five physical senses, thus "ordinary understanding, without which one is foolish or insane" (Latin sensus communis, Greek koine aisthesis); meaning "good sense" is from 1726. Also, as an adjective, commonsense.
commonality (n.): late 14c., "a community," from common (adj.), as if from Latin *communalitas. A respelling of commonalty (late 13c.). Meaning "the common people" is attested from 1580s; that of "state or quality of being shared" is from 1954.
commoner (n.): early 14c. (in commoners), from common (adj.).
commonly (adv.): c.1300, "in a way common to all," also "common to all;" also "usually," from common (adj.) + -ly (2).
commonplace (n.): 1540s, "a statement generally accepted," literal translation of Latin locus communis, from Greek koinos topos "general topic." See common (adj.) + place (n.). The adjectival sense of "having nothing original" dates from c.1600.
commonsensical (adj.): 1860, from common sense, with ending as in nonsensical, etc.
commonwealth (n.): late 15c., "public welfare, general good," from common (adj.) + wealth (n.); meaning "the state" is attested from 1510s; applied specifically to the government of England in the period 1649-1660.
commotion (n.): late 14c., from Middle French commocion "violent motion, agitation" (12c., Modern French commotion), from Latin commotionem (nominative commotio) "violent motion, agitation," noun of action from past participle stem of commovere "to move, disturb," from com- "together," or "thoroughly" (see com-) + movere "to move" (see move (v.)).
communal (adj.): 1811 in reference to communes; 1843 in reference to communities, from French communal (Old French comunal, 12c.), from Late Latin communalis, from communa (see commune (n.)).
communalism (n.): 1871 (in reference to Paris), from communal + -ism.
commune (v.): c.1300, "have dealings with," from Old French comuner "to make common, share" (10c., Modern French communier), from comun (see common (adj.)). Meaning "to talk intimately" is late 14c. Related: Communed; communing.
commune (n.): 1792, from French commune "small territorial divisions set up after the Revolution," from Middle French commune "free city, group of citizens" (12c.), from Medieval Latin communia, noun use of neuter plural of Latin adjective communis, literally "that which is common," from communis (see common (adj.)). The Commune of Paris usurped the government during the Reign of Terror. The word later was applied to a government on communalistic principles set up in Paris in 1871. Adherents of the 1871 government were Communards.
communicable (adj.): late 14c., from Old French communicable, from Late Latin communicabilis, from communicare (see communication).
communicate (v.): 1520s, "to impart" (information, etc.), from Latin communicatus, past participle of communicare "impart, inform" (see communication). Meaning "to share, transmit" (diseases, etc.) is from 1530s. Related: Communicated; communicating.
communication (n.): late 14c., from Old French comunicacion (14c., Modern French communication), from Latin communicationem (nominative communicatio), noun of action from past participle stem of communicare "to share, divide out; communicate, impart, inform; join, unite, participate in," literally "to make common," from communis (see common (adj.)).
communicative (adj.): late 14c., "that communicates," from French communicatif, from Latin communicat-, past participle stem of communicare "impart, inform" (see communication). Meaning "talkative" is recorded from 1650s.
communicator (n.): 1660s, from Latin communicator, agent noun from communicare (see communication).
communion (n.): late 14c., from Old French comunion "community, communion" (12c.), from Latin communionem (nominative communio) "fellowship, mutual participation, a sharing," used in Late Latin ecclesiastical language for "participation in the sacrament," from communis (see common (adj.)). Used by Augustine, in belief that the word was derived from com- "with, together" + unus "oneness, union."
communique (n.): 1852, from French communiqué, originally past participle of communiquer "to communicate" (14c.), from Latin communicare "impart, inform" (see communication). Originally the heading of official statements from the French government. Better, if it must be used in English, to print it with the accent.
communism (n.): "social system based on collective ownership," 1843, from French communisme (c.1840) from commun (Old French comun; see common (adj.)) + -isme (see -ism). Originally a theory of society; as name of a political system, 1850, a translation of German Kommunismus (itself from French), in Marx and Engels' "Manifesto of the Communist Party." Cf. communist. In some cases in early and mid-20c., a term of abuse implying anti-social criminality without regard to political theory.
Each [i.e. socialism, communism, anarchism] stands for a state of things, or a striving after it, that differs much from that which we know; & for many of us, especially those who are comfortably at home in the world as it is, they have consequently come to be the positive, comparative, & superlative, distinguished not in kind but in degree only, of the terms of abuse applicable to those who would disturb our peace. [Fowler]
communist: 1841, as both a noun and adjective, from French communiste (see communism). First attested in writing by John Goodwin Barmby (1820-1881), British Owenite and utopian socialist who founded the London Communist Propaganda Society in 1841. Main modern sense emerged after publication of Communist Manifesto ("Manifest der Kommunistischen Partei") in 1848. Shortened form Commie attested from 1940. Related: Communistic.
communitarian (n.): 1841, "member of a commune," from community + ending from utilitarian, etc. The adjective is attested from 1909.
community (n.): late 14c., from Old French comunité "community, commonness, everybody" (Modern French communauté), from Latin communitatem (nominative communitas) "community, society, fellowship, friendly intercourse; courtesy, condescension, affability," from communis "common, public, general, shared by all or many," (see common (adj.)). Latin communitatem "was merely a noun of quality ... meaning 'fellowship, community of relations or feelings,' but in med.L. it was, like universitas, used concretely in the sense of 'a body of fellows or fellow-townsmen' " [OED].

An Old English word for "community" was gemænscipe "community, fellowship, union, common ownership," from mæne "common, public, general," probably composed from the same PIE roots as communis. Community service as a criminal sentence is recorded from 1972, American English. Community college is recorded from 1959.
commutation (n.): mid-15c., from Old French commutacion "change, transformation, exchange, barter" (13c., Modern French commutation), from Latin commutationem (nominative commutatio) "a change, alteration," noun of action from past participle stem of commutare "to change, alter entirely" (see commute (v.)).
commutative (adj.): 1530s, from Medieval Latin commutativus, from Latin commutat-, past participle stem of commutare (see commute (v.)).
commutator (n.): 1839, agent noun in Latin form from Latin commutare (see commute (v.)).
commute (v.): mid-15c., "to change, transform," from Latin commutare "to often change, to change altogether," from com-, intensive prefix (see com-), + mutare "to change" (see mutable). Sense of "make less severe" is 1630s. Sense of "go back and forth to work" is 1889, from commutation ticket "season pass" (on a railroad, streetcar line, etc.), from commute in its sense of "to change one kind of payment into another" (1795), especially "to combine a number of payments into a single one." Related: Commuted; commuting.
commuter (n.): 1865, American English, "holder of a commutation ticket," agent noun from commute (v.).
Como: lake in Italy, named for the town along its shore, which is Roman Comum, from Celtic cumba "valley" (cf. coomb). Its ancient name was Lacus Larius; Lacus Comacinus begins to appear 4c. It is associated with Virgil and the two Plinys.
comorbidity (n.): 1985, from co- "along with" + morbidity "diseased condition." Comorbid (adj.) is a 1990 back-formation.
comp (n.): "complimentary ticket," 1885, short for complimentary. Meaning "nonpaying guest" is attested by 1930s; generalized to "anything given free" by 1960s. As a verb, by 1974. Related: Comped; comping. As a shortening of compensation (especially worker's/workman's) it was in use by 1970s.
compact (adj.): late 14c., from Middle French compact (14c.) or directly from Latin compactus "concentrated," past participle of compingere "to fasten together, construct," from com- "with, together" (see com-) + pangere "to fix, fasten" (see pact). Compact car is 1960. Compact disc is from 1979.
compact (n.1): "agreement," 1590s, from Latin compactum "agreement," noun use of neuter past participle of compacisci "come to agreement," from com- "together" (see com-) + pacisci "to covenant, contract" (see pact).
compact (v.): early 15c., from Latin compactus, past participle of compingere "to fasten together" (see compact (adj.)). Related: Compacted; compacting.
compact (n.2): "make-up case," 1921, from compact (adj.), based on its containing compacted face powder.
compaction (n.): late 14c., from Old French compaction, from Latin compactionem (nominative compactio) "a putting or joining together," noun of action from past participle stem of compingere (see compact (adj.)).
compadre (n.): "companion," 1834, American English, from Spanish compadre "godfather," hence "benefactor, friend," from Medieval Latin compater, from com- "with" (see com-) + pater "father" (see father (n.). Cf. compere, also gossip (n.).
companion (n.): c.1300, from Old French compagnon "fellow, mate, friend, partner" (12c.), from Late Latin companionem (nominative companio), literally "bread fellow, messmate," from Latin com- "with" (see com-) + panis "bread" (see food).

Found first in 6c. Frankish Lex Salica, and probably a translation of a Germanic word (cf. Gothic gahlaiba "messmate," from hlaib "loaf of bread"). Replaced Old English gefera "traveling companion," from faran "go, fare."
companionable (adj.): 1620s, from companion + -able. Related: Companionably; companionability.
companionship (n.): 1540s, from companion + -ship.
company (n.): mid-12c., "large group of people," from Old French compagnie "society, friendship, intimacy; body of soldiers" (12c.), from Late Latin companio (see companion). Meaning "companionship" is from late 13c. Sense of "business association" first recorded 1550s, having earlier been used in reference to trade guilds (c.1300). Meaning "subdivision of an infantry regiment" is from 1580s. Abbreviation co. dates from 1670s.
comparable (adj.): early 15c., from Middle French comparable, from Latin comparabilis "capable of comparison," from comparare (see comparison). Related: Comparably; comparability.
comparation (n.): late 15c., from Latin comparationem "a putting together," hence, "a comparing," noun of action from comparare (see comparison).
comparative (adj.): mid-15c., from Middle French comparatif, from Latin comparativus "pertaining to comparison," from comparat-, past participle stem of comparare (see comparison). Originally grammatical; general sense is from c.1600; meaning "involving different branches of a subject" is from 1670s. Related: Comparatively.
comparator (n.): 1883, agent noun in Latin form from compare.
compare (v.): late 14c., from Old French comparer (12c., Modern French comparer), from Late Latin comparare "to liken, to compare" (see comparison). Related: Compared; comparing. To compare notes is from 1708. Phrase without compare (attested from 1620s, but similar phrasing dates to 1530s) seems to be altered by folk etymology from compeer "rival."
comparison (n.): mid-14c., from Old French comparaison (12c.), from Latin comparationem (nominative comparatio), noun of action from past participle stem of comparare "make equal with, liken, bring together for a contest," literally "to couple together, to form in pairs," from com- "with" (see com-) + parare "prepare" (see pare).
compartment (n.): 1560s, from Middle French compartiment "part partitioned off" (16c.), through Italian compartimento, from Late Latin compartiri "to divide," from com-, intensive prefix (see com-), + partis, genitive of pars "part" (see part (n.)).
compartmental (adj.): 1831, from compartment + -al (1).