prefix meaning "two," O.E. twi-, prefix meaning "two, in two ways, twice, double," from P.Gmc. *twi- (cf. O.Fris. twi-, O.N. tvi-, Du. twee-, O.H.G. zwi-, Ger. zwei-), from PIE *dwis (cf. Skt. dvi-, Gk. di-, Old L. dvi-, L. bi-, Lith. dvi-), from *dwo "two" (see two). Cognate
with bi-. Older instances of it include M.E. twinter "two years old" (1404, of cattle, sheep, etc.), reduced from O.E. twi-wintre, and O.E. twispræc "double or deceitful speech."