preggo (adj.)

"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).

"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).