Geez

ˀəsma - because, since, in that; that is, namely; indeed, in fact (CDG 43)

For different ways of analysis see CDG 43. Leslau (ibid.) is inclined to connect ˀəsma with səm ‘name’.

PS
*ˀVSVm - because of, for the sake of (Arakelova 2001:30)
The sibilant is uncertain.
Both Akk. and Gez. forms are likely related to the noun *šVm- ‘name’.