Origins
The word 'pregnant' entered English in the early fifteenth century from Latin 'praegnΔns' (also spelβββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββled 'praegnΔs'), meaning 'with child.' The most widely accepted etymology derives the Latin word from 'prae-' (before) combined with the root of 'gnΔscΔ«' or 'nΔscΔ«' (to be born), giving a literal sense of 'in the state before birth.' The PIE root underlying 'gnΔscΔ«' is *Η΅enhβ-, meaning 'to give birth, to beget,' one of the most productive roots in the Indo-European family.
The root *Η΅enhβ- generated an extraordinary family of English words, all connected to birth and origin. Through Latin 'nΔscΔ«' (to be born), English received 'native' (born in a place), 'nascent' (being born, emerging), 'nature' (inborn quality, from 'nΔtΕ«ra'), 'nation' (those born together, a people), 'natal' (relating to birth), 'innate' (inborn), and 'renaissance' (rebirth). Through Latin 'genus' (birth, race, kind), it gave 'genus,' 'genre,' 'gender,' 'general,' 'generate,' 'generous,' 'genius,' and 'genuine.' Through Greek 'genos' (race, kind), it gave 'gene,' 'genesis,' 'genetic,' and 'genocide.' The word 'kin' and 'kind' come from the same root through the Germanic branch.
Before 'pregnant' became standard, English had several other terms for the condition. Old English used 'mid cilde' (with child) or 'bearnΔacen' (child-increased). Middle English added 'great with child' and 'enceinte' (borrowed from French). 'With child' remained the most common expression through the sixteenth century and appears frequently in the King James Bible. 'Pregnant' gradually displaced these older phrases in educated usage during the sixteenth and seventeenth centuries.
French Influence
There is a curious homonymic coincidence in English: a second word 'pregnant' exists, meaning 'compelling, cogent, significant,' as in Shakespeare's 'how pregnant sometimes his replies are' (Hamlet, 2.2). This second 'pregnant' has an entirely different origin β it comes from Old French 'preignant,' the present participle of 'preindre' (to press, to squeeze), from Latin 'premere.' The two words 'pregnant' are etymologically unrelated, having converged to identical spelling and pronunciation from different Latin sources. The 'compelling' sense is now archaic but survives in the phrase 'a pregnant pause,' where 'pregnant' means 'full of unspoken meaning.'
The verb 'impregnate' (to make pregnant; to saturate) entered English in the seventeenth century, from Late Latin 'impraegnΔre.' It has maintained both a literal biological sense and a figurative sense of filling or saturating something ('impregnated with resin'). The noun 'pregnancy' dates from the sixteenth century.
Social and linguistic taboos around pregnancy have produced an unusually rich vocabulary of euphemisms across English history. Besides the terms already mentioned, English has used 'expecting,' 'in a family way,' 'in a delicate condition,' 'with a bun in the oven,' and many others. The clinical directness of 'pregnant' itself was sometimes avoided in polite speech through the nineteenth century, with 'expecting' or 'in a condition' preferred. The twentieth century largely removed this taboo, and 'pregnant' is now used freely in all registers.