Huh, interesting. I learned a little hebrew (modern) and a few words of arabic. I know I learned "yes" in hebrew and thought I also did in arabic. However, as I understand it, arabic is more like many separate languages bound by some commonalities, so maybe that factor is what I am confused by.

As far as "oui" in french, that one I learned about and it's theorized (from memory, I may be a bit off) that it came from a contraction of two latin words meaning something like "it is so". The contraction originally started with a hard consonant but it fell off over time, leaving "oui". It is also an interesting read to look up!