I’m also from Galicia. First time I heard of (Busia) was when I visited U.S. The old timers (by that I mean 2nd 3rd 4th generation Poles) use that in their speech. Yes a lot of them were from that region of Poland, but it seems to apply only to the families where Polish was a second language used at home or not spoken at all. Since enough people use it I guess it makes it a word. Personally I think it’s cute and it emphasizes their heritage. This is something to be proud of not frowned upon.
Franek:
She refered to me as her maly Nunczek.
Franek it’s “Wnuczek” not “Nuczek” but close enough and it means grandson.