When did you first learn about "Ussins and Themmins"?

For me it wasn't until I was around 12; I was outside mucking around and a group of older kids went around my street asking us if we were catholic or protestant. I'd no clue what I was until one of my mates said "He's a protestant". Asked my ma that night what a catholic was and was it a bad thing to be one 😂 Never went to Church and I went to an Integrated Primary school so I had no clue.. but it explained why some kids in the class went to a different RE lesson that some of us 🙃