@DamkerngT. Check out
this answer that I posted on ELU. I think you're right that "of" doesn't mean "from", but its ancient root meant something very much like "away from", and this still shows up in various modern usages. Really, though, regarding the question about "ask something of somebody", it's probably best to just think of "of" as English's general-purpose, catch-all preposition, capable of meaning any relationship at all.