a combining form meaning “two,” “twice”: twibill.

Origin of twi-

Middle English, Old English; cognate with German zwie- (Old High German zwi-), Latin bi-, Greek di-. See two Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Word Origin and History for twi-

word-forming element meaning "two," Old English twi-, prefix meaning "two, in two ways, twice, double," from Proto-Germanic *twi- (cf. Old Frisian twi-, Old Norse tvi-, Dutch twee-, Old High German zwi-, German zwei-), from PIE *dwis (cf. Sanskrit dvi-, Greek di-, Old Latin dvi-, Latin bi-, Lithuanian dvi-), from *dwo "two" (see two). Cognate with bi-. Older instances of it include Middle English twinter "two years old" (c.1400, of cattle, sheep, etc.), reduced from Old English twi-wintre, and Old English twispræc "double or deceitful speech."

Online Etymology Dictionary, © 2010 Douglas Harper