Translation:Slàinte, a mhàthair!
In Irish it's needed to show you're in the vocative case (when you're addressing them... Think "O, Romeo"). So I assume it is similar just with looser usage.
For the record, in Irish it makes names like Séamus become Shéamus, (which is pronounced liked the Scottish equivalent Hamish) and idk if Scottish does that too as they've seemed to stick with names starting with vowels so far.