Geebag

n.

Heard in Mayo, Dublin and Galway

An obnoxious, unpleasant, or stupid person, often applied as a general insult.

In use

Yer a geebag lad for cursin' in front of the parish priest!

Posh English

You are a perfect idiot, my good fellow, for uttering profanities before the clergyman.

Same phrase, other counties