"a fast grandmother."
I know Robert Burns called his sheepdog Luath, after Cuchullin's dog - even though he lived in a non-Gaelic area. It's a great name for a sheepdog. And I also realised why the Luath Press in Edinburgh uses a sheepdog (Border collie) as its logo - founded in Ayrshire, so called after RB's dog. I'd just never thought about it before.
It gets a schwa in there, because Gàidhlig doesn't allow consonants that don't form a sound of their own to be together without one, even if in the spelling they are. Sc, sg, ch, etc are their own sounds, but lb in Alba for example, gets the schwa, nm in ainm gets its, nmh in seanmhair gets it, and so on. You can hear this in Irish English to this day with words like 'film' (fil-im).
You just have to go with it. You can think of the 'n' as being a little elongated drawn out sound, more like a 'nuh' and then the 'mh' is pronounced as a 'v' sound like 'bh' is also pronounced as a 'v' in some words. It's a new language with its own logic that we will wrap our heads round eventually!