Even though the Usenet is pretty much on its way out, I still follow a number of newsgroups and among them is "soc.genealogy.ireland" and others. Today an individual in that group posted a comment on Irish citizenship and obtaining an Irish Passport. Just in passing he used a phrase I had not heard in quite a while. It was, "Which foot you dig with" which means "which religion are you - Protestant or Catholic." Catholics dig with their right foot, the same hand they bless themselves, and Protestants dig with their left. Of course Catholics dig with both their right and left depending which way their brain is wired but the phrase is still used although now rarely.
In a similar vein, although I don't know if it is limited to the Irish, is to refer to non-Catholics as 'left-handers.' Again, Catholics would be 'right-handers' as they use their right hands to bless themselves. I can recall both my mother and father using this term and I'm sure they would describe our friend and neighbor, Helen Neary, as a 'left hander.' I can't recall the last time that I have heard this term.