You probably figured out what today’s word is.
Fry showed up in the late thirteenth century, from the Old French frire (same meaning, so I guess they had fried food back then). I can totally see why they changed that. Too many R’s in a row there. Anyway, before frire, there was the classical Latin frigere, again, same meaning, and even further back there’s the Proto Indo European bher-, cook or bake (among other things; bher is the verse- of Proto Indo European, meaning it was everywhere, and so a lot of English words stem from it). Yes, it really did switch from b to f. That’s language for you.
University of Texas at Austin Linguistic Research Center