swill v.

"ingest through the throat" (transitive), Old English swelgan "swallow, imbibe, absorb" (class III strong verb; past tense swealg, past participle swolgen), from Proto-Germanic *swelgan/*swelhan (source also of Old Saxon farswelgan, Old Norse svelgja "to swallow," Middle Dutch swelghen, Dutch zwelgen "to gulp, swallow," Old High German swelahan "to swallow," German schwelgen "to revel"), probably from PIE root *swel- (1) "to eat, drink" (source also of Iranian *khvara- "eating").

Intransitive sense "perform the act of swallowing" is from c. 1700. Sense of "consume, destroy" is attested from mid-14c. Meaning "to accept without question" is from 1590s. Related: Swallowed; swallowing.