Never try to understand how gaelic words came to be spelled the way they are. That way madness lies.
For instance, bh is clearly a V as in Siobhan. GUESS AGAIN because mh is V in Niamh! It makes zero sense. I lived in Scotland for 8 years, during which time I learned the hard way to just smile, nod, and pretend everything is fine. (Presumably it has something to do with confounding the English, but I’m not certain on that theory)