Latin word bini comes from Proto-Indo-European *dwó, and later Proto-Indo-European *dwís (In two. Twice, doubly.)

Detailed word origin of bini

Dictionary entry	Language	Definition
*dwó	Proto-Indo-European (ine-pro)
*dwís	Proto-Indo-European (ine-pro)	In two. Twice, doubly.
s	Latin (lat)
bini	Latin (lat)