I'm not sure what the problem is supposed to be here. As I'm fond of telling people, in Spanish, there is a phrase "ojala que" which translates to something like "I hope that...." But literally, it comes from an Arabic phrase meaning "may Allah will that...." I'm not sure that anyone so much cares that the expression originates from a time when the Muslims ruled portions of the Iberian Peninsula. It's just an expression.
Similarly, I'm not sure that it should be so surprising that there are colloquialisms in English that reflect the fact that English has long been a language of some god believing folks. I'm sure I'm not the only atheist that still uses phrases like "oh my God," "God knows" and especially "God damn it."
So people say "rest in peace." Who really cares? I've got five percenter homies that say "rest in power." It's all whatever. The dead are dead. In any case, I always end my shit the same way: