"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).
prefiguration
prefigure
prefix
preflight
preformed
preggers
preggo
preglacial
pregnable
pregnancy
pregnant
)window.location='https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=byronic106@yahoo.com&lc=US&item_name=Donation+to +Help+Keep+Etymonline+Free+and+Open&no_note=0&cn=&curency_code=USD&bn=PP-DonationsBF:btn_donateCC_LG.gif:NonHosted'){kind=link}