For some reason, the way the name
Fionnuala looks has always reminded me of some sort of cleaning liquid. For that reason, I have never liked it. However, that is a personal association, the origin of which is obscure even to myself, and the name does have the benefit of a cute nickname,
Finn. But then, that brings up fish associations...perhaps I am overthinking this one.
I really like
Oona, but I think it's even cuter spelled
Una.