Anglo-Celtic refers to people who come from a mix of two big groups of people: Anglo-Saxons and Celts. The Anglo-Saxons were a group of people from Germany who took over England a long long time ago. And the Celts were another group of people who come from places like Ireland and Scotland. So when we talk about Anglo-Celtic people, we mean people who might have ancestors from both of those groups. It's like saying one of your parents is from Germany and the other is from Ireland - you're a mix of those two cultures!