An Etymological Dictionary of the German Language/Annotated/sinken
sinken, verb, ‘to sink, fall, abate,’ from the equivalent Middle High German sinken, Old High German sinchan; a common Teutonic strong verb (for its causative see senken). Compare Gothic sigqan, Old Icelandic sokkra, Anglo-Saxon sincan, English to sink, Dutch zinken, Old Saxon sincan. The a-root senq, contained in these words, seems to have originated in an i-root sī̆q, which appears in the parallel form sī̆hw in Modern High German seihen, as well as Old High German sîgan, Middle High German sîgen, ‘to drip.’ The pre-Teutonic root sig, siq appears in Old Slovenian sĭcati, ‘to make water,’ sĭčĭ}, ‘urine,’ as well as in Sanscrit sic, ‘to wet, pour out,’ whose present appears in a nasalised form Modern High German seihen is based upon Teutonic saik, pre-Teutonic síg.