Online Etymology Dictionary

pregnant (adj.2): "convincing, weighty, pithy," late 14c., "cogent, convincing, compelling" (of evidence, an argument, etc.); sense of "full of meaning" is from c.1400. According to OED from Old French preignant, present participle of preindre "press, squeeze, stamp, crush," from earlier priembre, from Latin premere "to press" (see press (v.1)). But Watkins has it from Latin praehendere "to grasp, seize," and in Barnhart it is from Latin praegnans "with child," literally "before birth" and thus identical with pregnant (adj.1).
pregnant (adj.1): "with child," early 15c., from Latin praegnantem (nominative praegnans, originally praegnas) "with child," literally "before birth," probably from prae- "before" (see pre-) + root of gnasci "be born" (see genus).

Retained its status as a taboo word until c.1950; modern euphemisms include anticipating, enceinte, expecting, in a family way, in a delicate (or interesting) condition. Old English terms included mid-bearne, literally "with child;" bearn-eaca, literally "child-adding" or "child-increasing;" and geacnod "increased." Among c.1800 slang terms for "pregnant" was poisoned (in reference to the swelling).
preheat (v.): also pre-heat, 1878, from pre- + heat (v.). Related: Preheated; preheating.
prehensile (adj.): 1771, from French préhensile "adapted for grasping" (Buffon), from Latin prehensus, past participle of prehendere "to grasp, to seize," from prae- "before" (see pre-) + -hendere, related to hedera "ivy," via notion of "clinging," and cognate with Greek khandanein "to take in, hold" (see get (v.)).
prehension (n.): 1530s, "seizure, arrest," from Latin prehensionem (nominative prehensio), noun of action from past participle stem of prehendere (see prehensile). Use in philosophy is from 1925.
prehistoric (adj.): 1832, modeled on French préhistorique; see pre- + historic.
prehistory (n.): 1869, perhaps a back-formation from prehistoric. Related: Prehistorian.
prejudge (v.): 1560s, from French préjuger (16c.), equivalent to Latin praejudicare "to judge beforehand;" see pre- + judge (v.). Related: Prejudged; prejudging; prejudgment.
prejudice (n.): c.1300, "despite, contempt," from Old French prejudice "prejudice, damage" (13c.), from Medieval Latin prejudicium "injustice," from Latin praeiudicium "prior judgment," from prae- "before" (see pre-) + iudicium "judgment," from iudex (genitive iudicis) "a judge" (see judge (v.)). Meaning "injury, physical harm" is mid-14c., as is legal sense "detriment or damage caused by the violation of a legal right." Meaning "preconceived opinion" (especially but not necessarily unfavorable) is from late 14c. in English.
prejudice (v.): mid-15c., "to injure or be detrimental to," from prejudice (n.). The meaning "to affect or fill with prejudice" is from c.1600. Related: Prejudiced; prejudicing.
prejudicial (adj.): early 15c., "causing prejudice;" 1530s, "full of prejudice," from prejudice (n.) + -al (1), or else from Middle French prejudicial and directly from Medieval Latin prejudicialis "injurious," from Latin praeiudicium.
prelapsarian (adj.): "pertaining to the condition before the Fall," 1834, from pre- + Latin lapsus "a fall" (see lapse (v.)) + ending from unitarian, etc.
prelate (n.): c.1200, from Old French prelat (Modern French prélate) and directly from Medieval Latin prelatus "clergyman of high rank," from Latin praelatus "one preferred," noun use of past participle of praeferre (see prefer), from prae "before" (see pre-) + latus "borne, carried" (see oblate (n.)).
prelim (n.): 1891, short for preliminary (race, test, event, etc.).
preliminary (adj.): 1660s, from French préliminaire and directly from Medieval Latin praeliminaris, from Latin prae- "before" (see pre-) + limen (genitive liminis) "threshold" (see limit (n.)). A word that arose in reference to negotiations to end the Thirty Years' War. Earliest attested form in English is preliminaries (n.), 1650s.
prelude (n.): 1560s, from Middle French prélude "notes sung or played to test the voice or instrument" (1530s), from Medieval Latin preludium "prelude, preliminary," from Latin praeludere "to play beforehand for practice, preface," from prae- "before" (see pre-) + ludere "to play" (see ludicrous). Purely musical sense first attested in English 1650s. Related: Prelusion.
premarital (adj.): also pre-marital, 1863, from pre- + marital. Phrase pre-marital sex attested from 1953.
premature (adj.): mid-15c., from Latin praematurus "early ripe" (as fruit), "too early, untimely," from prae "before" (see pre-) + maturus "ripe, timely" (see mature (v.)). Related: Prematurely; prematurity; prematuration. Premature ejaculation is attested from 1848; Latin euphemism ejaculatio praecox dates to 1891 in English but was used earlier in German and appears to have been, at first at least, the psychologist's term for it.
premedical (adj.): also pre-medical, 1881, in reference to study for medical training, from pre- + medical.
premeditate (v.): 1540s, from pre- + meditate, or a back formation from premeditation, or else from Latin praemeditatus, past participle of praemeditari "to think over." Related: Premeditated; premeditating.
premeditation (n.): early 15c., from Old French premeditacion and directly from Latin praemeditationem (nominative praemeditatio) "consideration beforehand," noun of action from past participle stem of praemeditari "to consider beforehand," from prae- "before" (see pre-) + meditari "to consider" (see meditation).
premenstrual (adj.): also pre-menstrual, 1865, from pre- + menstrual. Premenstrual syndrome (1971) earlier was premenstrual tension (1928).
premier (adj.): mid-15c., "first in time;" late 15c. as "first in rank," from Middle French premier "first, chief," from Latin primarius "of the first rank, chief" (see primary (adj.)).
premier (n.): 1711 in the political sense, a shortening of premier minister (1680s); see premier (adj.). In U.S. usage, premier formerly was applied occasionally to the Secretary of State (1855-c.1900).
premiere (n.): 1889, "first performance of a play," from French première, in phrase première représentation, from fem. of Old French premier "first" (see premier). The verb is recorded from 1940.
premillennial (adj.): 1829, "before the millennium," especially in theological sense of "before the Second Coming of Christ;" from pre- + millennial. Premillenarian, one who believes the second coming of Christ will precede the Millennium, is from 1842. Related: Premillenialism.
premise (n.): late 14c., in logic, "a previous proposition from which another follows," from Old French premisse (14c.), from Medieval Latin premissa (propositio or sententia) "(the proposition) set before," noun use of fem. past participle of Latin praemittere "send forward, put before," from prae "before" (see pre-) + mittere "to send" (see mission). In legal documents it meant "matter previously stated" (early 15c.), which in deeds or wills often was a house or building, hence the extended meaning "house or building, with grounds" (1730).
premise (v.): "to state before something else," mid-15c., from premise (n.). Related: Premised; premising.
premises (n.): "building and grounds," 1730; see premise (n.).
premium (n.): c.1600, "reward given for a specific act," from Latin praemium "reward, profit derived from booty," from prae- "before" (see pre-) + emere "to buy," originally "to take" (see exempt (adj.)). Insurance sense is 1660s, from Italian premio. Adjectival sense of "superior in quality" is first attested 1925, originally in reference to butter.
premolar (n.): "premolar tooth," 1841, from pre- + molar. Related: Premolars.
premonition (n.): mid-15c., from Anglo-French premunition, Middle French premonicion, from Late Latin praemonitionem (nominative praemonitio) "a forewarning," noun of action from past participle stem of Latin praemonere "forewarn," from prae "before" (see pre-) + monere "to warn" (see monitor (n.)).
premonitory (adj.): 1640s, from Late Latin praemonitorius, from praemonitor, agent noun from stem of praemonere (see premonition).
premorbid (adj.): also pre-morbid, 1905, from pre- + morbid.
premotion (n.): 1640s, from medical Latin praemotionem (nominative praemotio), noun of action from past participle stem of Late Latin praemovere, from prae- (see pre-) + movere "to move" (see move (v.)).
prenatal (adj.): 1826, formed in English from pre- + natal.
prentice (n.): c.1300, shortened form of apprentice (n.). As a verb from 1590s.
prenup (n.): by 1988 as a shortening of prenuptial agreement (see prenuptial).
prenuptial (adj.): 1826, from pre- + nuptial. Prenuptial agreement first recorded 1833.
preoccupancy (n.): also pre-occupancy, "prior occupation," 1734, from pre- + occupancy.
preoccupation (n.): 1550s, "state of occupying beforehand," from Latin praeoccupationem (nominative praeoccupatio) "a seizing beforehand, anticipation," noun of action from past participle stem of praeoccupare, from prae- "before" (see pre-) + occupare "seize" (see occupy). Meaning "mental absorption" is from 1854. Earlier its secondary sense was "bias, prejudice" (c.1600).
preoccupied (adj.): "absorbed in thought," 1823, past participle adjective from preoccupy (v.). Earlier it meant "occupied in advance."
preoccupy (v.): 1560s, from pre- + occupy. Related: Preoccupied; preoccupying.
preordain (v.): 1530s, from pre- + ordain (q.v.). Related: Preordained; preordaining.
prep (n.): 1862, short for preparation. Prep school attested from 1895, short for preparatory school. First record of prep in the sense "student or graduate of a preparatory school" is from 1899 (also see preppie).
prep (v.): slang shortening of prepare, 1908. Related: Prepped; prepping.
preparation (n.): late 14c., "act of preparing," from Latin praeparationem (nominative praeparatio) "a making ready," noun of action from past participle stem of praeparare "prepare," from prae "before" (see pre-) + parare "make ready" (see pare). Meaning "a substance especially prepared" is from 1640s.
preparatory (adj.): early 15c., from Late Latin praeparatorius, from Latin praeparatus (see preparation). Earlier in same sense was preparative (late 14c.). Applied from 1822 to junior schools in which pupils are "prepared" for a higher school.
prepare (v.): mid-15c., a back formation from preparation and in part from Middle French preparer (14c.), from Latin praeparare "make ready beforehand" (see preparation). Related: Prepared; preparing. Be prepared as the Boy Scouts' motto is attested from 1911.
preparedness (n.): 1580s, from prepared + -ness.