Haffa Jaffa
Someone who has one protestant and one non-protestant parent. Protestants are often called "orange-men" due to William of Orange and the Orange Order so if you're half an orange-man you're a "Haffa Jaffa" or "Half a Jaffa" as in a Jaffa Cake - an orange flavoured biscuit.
Person A: Did you hear Rory is a Haffa Jaffa?
Person B: Really?
Person A: Yeah, his da's a prod and his ma's a Catholic.
Person B: Really?
Person A: Yeah, his da's a prod and his ma's a Catholic.