O.E. sincan "become submerged, go under" (past tense sanc, pp. suncen), from P.Gmc. *senkwanan (cf. O.S. sinkan, O.N. sökkva, M.Du. sinken, Du. zinken, O.H.G. sinkan, Ger. sinken, Goth. sigqan), from PIE base *sengw- "to sink." The transitive use supplants M.E. sench (cf. drink/drench) which died out 14c. Sinking fund is from 1724; sinker in fishing line sense is from 1844. Adjective phrase sink or swim is from 1668. To sink without a trace is WWI military jargon, transl. Ger. spurlos versenkt.