An Etymological Dictionary of the German Language/Annotated/zwie-

by Friedrich Kluge

zwie-, in compounds ‘two,’ from Middle High German and Old High German zwi-, Low German twi-, Dutch twee-, Old Icelandic tuî-, Anglo-Saxon twi-, Gothic *tvi-. It is the form of the numeral zwei as the first element of a compound; compare in the non-Teutonic languages δι- (from δϝι-), Latin bi-, Sanscrit dvi-, used in a similar way.