Etymology
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pregnant (adj.2)

["convincing, weighty, pithy, full of meaning"] late 14c., "cogent, convincing, compelling" (of evidence, an argument, etc.); c. 1400 as "full of meaning;" from Old French preignant "pregnant, pithy, ready capable," which is probably from Latin praegnans "with child, pregnant, full" and thus the same word as pregnant (adj.1).

All uses seem to be derivable from the sense of "with child." But in some sources this English pregnant has been referred to French prenant, present participle of prendre "to take," or to the French present participle of preindre "press, squeeze, stamp, crush," from earlier priembre, from Latin premere "to press, hold fast, cover, crowd, compress." The two English adjectives are so confused as to be practically one word, if they were not always so.

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pregnant (adj.1)

"with child, impregnated, that has conceived in the womb," 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" (from PIE root *gene- "give birth, beget").

The word tended to be avoided in polite conversation 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).

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preggo (adj.)

"pregnant," Australian slang, 1951, from pregnant (adj.1). Compare preggers.

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pregnancy (n.)

"state of a female who has conceived or is with child," 1520s (originally figurative), from pregnant (adj.1) + abstract noun suffix -cy. Literal use attested from 1590s. An earlier word in this sense was pregnacioun (early 15c.), from Old French pregnacion and Latin praegnationem.

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impregnate (v.)
c. 1600, "to fill with an ingredient, spirit, etc.;" 1640s as "make (a female) pregnant), from Late Latin impraegnatus "pregnant," past participle of impraegnare "to render pregnant," from assimilated form of in- "into, in" (from PIE root *en "in") + praegnare "make pregnant" (see pregnant). Earlier in same sense was impregn (1530s), which OED marks as "now only in poetic use."
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preggers (adj.)

"pregnant," 1942, British slang, from pregnant (adj.1) + ending as in bonkers, crackers, starkers. This seems to be an expanded version of -er (3), the suffix used to make jocular or familiar formations from common or proper names (as in rugger for rugby, and soccer).

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*per- (4)

Proto-Indo-European root meaning "to strike," an extended sense from root *per- (1) "forward, through."

It forms all or part of: compress; depress; espresso; express; impress (v.1) "have a strong effect on the mind or heart;" imprimatur; imprint; oppress; oppression; pregnant (adj.2) "convincing, weighty, pithy;" press (v.1) "push against;" pressure; print; repress; reprimand; suppress.

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pregnable (adj.)

of a fortress, etc., "capable of being taken or won by force," 1530s, an alteration of Middle English preignable, earlier prenable (early 15c.), pernable (late 14c.), from Old French prenable, pregnauble "assailable, vulnerable," from stem of prendre "to take, grasp, seize," from Latin prehendere "to take hold of, to seize" (from prae- "before," see pre-, + -hendere, from PIE root *ghend- "to seize, take"). The form was confused in French and English by the influence of unrelated words from French preignaunt and English pregnant.

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*gene- 

*genə-, also *gen-, Proto-Indo-European root meaning "give birth, beget," with derivatives referring to procreation and familial and tribal groups.

It forms all or part of: Antigone; autogenous; benign; cognate; congener; congenial; congenital; connate; cosmogony; cryogenic; degenerate; engender; engine; epigone; eugenics; -gen; gendarme; gender; gene; genealogy; general; generate; generation; generic; generous; genesis; -genesis; genial; -genic; genital; genitive; genius; genocide; genotype; genre; gens; gent; genteel; gentile; gentle; gentry; genuine; genus; -geny; germ; german (adj.) "of the same parents or grandparents;" germane; germinal; germinate; germination; gingerly; gonad; gono-; gonorrhea; heterogeneous; homogeneous; homogenize; homogenous; impregnate; indigenous; ingenious; ingenuous; innate; jaunty; kermes; kin; kindergarten; kindred; king; kind (n.) "class, sort, variety;" kind (adj.) "friendly, deliberately doing good to others;" Kriss Kringle; malign; miscegenation; nada; naive; nascent; natal; Natalie; nation; native; nature; nee; neonate; Noel; oncogene; ontogeny; photogenic; phylogeny; pregnant (adj.1) "with child;" primogenitor; primogeniture; progenitor; progeny; puisne; puny; renaissance; theogony; wunderkind.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit janati "begets, bears," janah "offspring, child, person," janman- "birth, origin," jatah "born;" Avestan zizanenti "they bear;" Greek gignesthai "to become, happen," genos "race, kind," gonos "birth, offspring, stock;" Latin gignere "to beget," gnasci "to be born," genus (genitive generis) "race, stock, kind; family, birth, descent, origin," genius "procreative divinity, inborn tutelary spirit, innate quality," ingenium "inborn character," possibly germen "shoot, bud, embryo, germ;" Lithuanian gentis "kinsmen;" Gothic kuni "race;" Old English cennan "beget, create," gecynd "kind, nature, race;" Old High German kind "child;" Old Irish ro-genar "I was born;" Welsh geni "to be born;" Armenian cnanim "I bear, I am born."

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gravid (adj.)

"pregnant," 1590s, from Latin gravidus "loaded, full, swollen; pregnant with child," from gravis "burdened, heavy," from PIE root *gwere- (1) "heavy." Related: Gravidity. Gravidation "pregnancy" is attested from mid-15c.

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