An Etymological Dictionary of the German Language/zwie-

by Friedrich Kluge

zwie-, in compounds ‘two,’ from MidHG. and OHG. zwi-, LG. twi-, Du. twee-, OIc. tuî-, AS. twi-, Goth. *tvi-. It is the form of the numeral zwei as the first element of a compound; comp. in the non-Teut. languages δι- (from δϝι-), Lat. bi-, Sans. dvi-, used in a similar way.