I think it should be mo buachaill. In Irish the address form requires the insertion of an h after the first letter excluding r, l an n, but since it's "my boy" as opposed to just "boy" I'm not sure that would that would apply. I;m not sure if the personal pronoun "mo" causes aspiration or not. This would make it (BOOH-a-hill) as opposed to (VOOH-a-hill) with a hint oh a c-sound at the beginning of the last syllable. At any rate, I'm just learning the language, so don't take my word for granted. Rich