sink (v.)

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 (mid-13c.) supplanted Middle English sench (compare drink/drench) which died out 14c. Related: Sank; sunk; sinking. Sinking fund is from 1724. Adjective phrase sink or swim is from 1660s. To sink without a trace is World War I military jargon, translating German spurlos versenkt.

sink (n.)

early 15c., "cesspool, pit for reception of wastewater or sewage," from sink (v.). Figurative sense of "place where corruption and vice abound" is from 1520s. Meaning "drain for carrying water to a sink" is from late 15c. Sense of "shallow basin (especially in a kitchen) with a drainpipe for carrying off dirty water" first recorded 1560s. In science and technical use, "place where heat or other energy is removed from a system" (opposite of source), from 1855.

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Definitions of sink from WordNet
sink (v.)
fall or descend to a lower place or level;
He sank to his knees
Synonyms: drop / drop down
sink (v.)
cause to sink;
The Japanese sank American ships in Pearl Harbor
sink (v.)
pass into a specified state or condition;
He sank into nirvana
Synonyms: pass / lapse
sink (v.)
go under;
The raft sank and its occupants drowned
Synonyms: settle / go down / go under
sink (v.)
descend into or as if into some soft substance or place;
He sank into bed
Synonyms: subside
sink (v.)
appear to move downward;
The setting sun sank below the tree line
Synonyms: dip
sink (v.)
fall heavily or suddenly; decline markedly;
Synonyms: slump / fall off
sink (v.)
fall or sink heavily;
My spirits sank
Synonyms: slump / slide down
sink (v.)
embed deeply;
She sank her fingers into the soft sand
Synonyms: bury
sink (n.)
plumbing fixture consisting of a water basin fixed to a wall or floor and having a drainpipe;
sink (n.)
(technology) a process that acts to absorb or remove energy or a substance from a system;
the ocean is a sink for carbon dioxide
sink (n.)
a depression in the ground communicating with a subterranean passage (especially in limestone) and formed by solution or by collapse of a cavern roof;
Synonyms: sinkhole / swallow hole
sink (n.)
a covered cistern; waste water and sewage flow into it;
Synonyms: cesspool / cesspit / sump