c. 1300, "belonging to all, owned or used jointly, general, of a public nature or character," from Old French comun "common, general, free, open, public" (9c., Modern French commun), from Latin communis "in common, public, shared by all or many; general, not specific; familiar, not pretentious." This is from a reconstructed PIE compound *ko-moin-i- "held in common," compound adjective formed from *ko- "together" + *moi-n-, suffixed form of root *mei- (1) "to change, go, move," hence literally "shared by all."

The second element of the compound also is the source of Latin munia "duties, public duties, functions," those related to munia "office." Perhaps reinforced in Old French by the Germanic form of PIE *ko-moin-i- (compare German gemein, Old English gemne "common, public, general, universal;" see mean (adj.)), which came to French via Frankish.

Used disparagingly of women and criminals since c. 1300. Meaning "pertaining equally to or proceeding equally from two or more" is from c. 1400. Meaning "usual, not exceptional, of frequent occurrence" is from late 14c. Sense of "not distinguished, belonging to the general mass" is from c. 1400; of things, "ordinary, not excellent," late 14c.

Common pleas is 13c., from Anglo-French communs plets, hearing civil actions by one subject against another as opposed to pleas of the crown. Common prayer is that done in public in unity with other worshipers; contrasted with private prayer. Common stock is attested from 1888. Common speech (late 14c.) is the vernacular, as opposed to Latin. Common good (late 14c.) translates Latin bonum publicum "the common weal." The college common room (1660s) is one to which all members have common access. 

1560s, "heliotrope," from sun (n.) + flower (n.). In reference to the Helianthus (introduced to Europe 1510 from America by the Spaniards) it is attested from 1590s, so called from the appearance of the heads.

c. 1300, "a fellowship or brotherhood; early 14c., "people of a community or town, freemen, citizenry;" late 15c., "land held in common," from Old French commune and Medieval Latin communia, and partly from common (adj.). Also compare commons. Latin communis "common, general" (adj.) also served as a noun meaning "common property; state, commonwealth."

1839, from common sense, with ending as in nonsensical, etc. Common-sensible is attested from 1848.

1580s, "a sunflower," also the name of a type of opal, from Italian girasole "sunflower," literally "turning toward the sun," from girare "to rotate" (see gyre (n.)) + sole (from PIE root *sawel- "the sun").

holy city in ancient Judea, from Greek Hierousalem, from Hebrew Yerushalayim, literally "foundation of peace," from base of yarah "he threw, cast" + shalom "peace." Jerusalem "artichoke" is folk etymology of Italian girasole "sunflower" (see girasole).

c. 1300, "in a way common to all," also "common to all;" also "usually, generally," from common (adj.) + -ly (2).

late 14c. (mid-14c. in Anglo-French), "one of the common people, a member of the third estate," agent noun from common (v.) "participate in common, associate or have dealings with" (mid-14c.), from common (adj.). From mid-15c. as "member of the House of Commons."

"characteristic of the common people," 1914, from folk + -y (2). Old English had folcisc "popular, secular, common."

1844, American English, from Spanish incomunicado, past participle of incomunicar "deprive of communication," from in- "not" (see in- (1)) + comunicar "communicate," from Latin communicare "to share, impart," literally "to make common," related to communis "common, public, general" (see common (adj.)).