sinkhole n.

early 15c., "cesspool, pit for reception of wastewater or sewage," from sink (v.). The meaning "drain for carrying water to a sink" is from late 15c., and the sense of "shallow basin (especially in a kitchen) with a drainpipe for carrying off dirty water" is by 1560s.

The figurative sense of "place where corruption and vice abound, abode or resort of depraved or debauched persons" is from 1520s.  In science and technical use, "place where heat or other energy is removed from a system" (opposite of source), from 1855, from the notion of sink as "receptacle of waste matter."

Old English hol (adj.) "hollow, concave;" as a noun, "hollow place; cave; orifice; perforation," from Proto-Germanic *hulan (source also of Old Saxon, Old Frisian, Old High German hol, Middle Dutch hool, Old Norse holr, German hohl "hollow," Gothic us-hulon "to hollow out"), from PIE root *kel- (1) "to cover, conceal, save." As an adjective, it has been displaced by hollow, which in Old English was only a noun, meaning "excavated habitation of certain wild animals."

As a contemptuous word for "small dingy lodging or abode" it is attested from 1610s. Meaning "a fix, scrape, mess" is from 1760. Obscene slang use for "vulva" is implied from mid-14c. Golfing hole-in-one is from 1914; as a verbal phrase from 1913. To need (something) like a hole in the head, applied to something useless or detrimental, first recorded 1944 in entertainment publications, probably a translation of a Yiddish expression such as ich darf es vi a loch in kop.

Middle English sinken, from Old English sincan (intransitive) "become submerged, go under, subside" (past tense sanc, past participle suncen), from Proto-Germanic *senkwan (source also of Old Saxon sinkan, Old Norse sökkva, Middle Dutch sinken, Dutch zinken, Old High German sinkan, German sinken, Gothic sigqan), from PIE root *sengw- "to sink."

The transitive use "force or drag gradually downward" (attested from late 12c.) supplanted Middle English sench (compare drink/drench) which died out 14c. The sense of "go in, penetrate" (of a blow, a weapon, etc.) is from c. 1300; by early 14c. as "make a penetrating impression on the mind." Related: Sank; sunk; sinking.

From early 14c. as "be reduced to a lower or worse state;" late 14c. as "fall or fail as from weakness or under a heavy blow." From 1590s as "decrease, be reduced in value, amount, etc." Of the sun, moon, etc., "to set," c. 1600. Of land, "dip downward gradually," by 1726.

Contrasted with swim (v.) since 14c.; the adjectival phrase sink or swim is from 1660s. To sink without a trace is World War I military jargon, translating German spurlos versenkt.