c. 1600, "act of pouring or rushing back," chiefly medical (of blood, digestive fluid, etc.), from Medieval Latin regurgitationem (nominative regurgitatio), noun of action from past-participle stem of regurgitare "to overflow," from re- "back" (see re-) + Late Latin gurgitare "engulf, flood" (found in Latin ingurgitare "to pour in"), from gurges "whirlpool, gorge, abyss" (see gurges).
1640s (intransitive), of fluids, "to surge or rush back, be poured back," a back formation from regurgitation, or else from Medieval Latin regurgitatus, past participle of regurgitare. Transitive sense of "to vomit, cast out from the stomach" is attested by 1753. Related: Regurgitated; regurgitating.