Latin word ob- comes from Proto-Indo-European *h₁epi (On, at, near.)

Detailed word origin of ob-

Dictionary entry	Language	Definition
*h₁epi	Proto-Indo-European (ine-pro)	On, at, near.
ob	Latin (lat)	Against; facing. In the direction of, to, towards. On account of, according to, because of, due to, for (the purpose of).
ob-	Latin (lat)	Towards; against.

Words with the same origin as ob-