In the year 449 Germanic tribes arrived in Britain from the European mainland, and displaced the native British (Celtic) population, eventually establishing a single language which was Anglo-Saxon in character.^*

When you have people like the Irish, Welsh, or Scots proclaiming their heritage, particularly against those Anglo-Saxon English bastards, it's easy to think of the Celts like this: People who were living their lives in the British Isles until they were overrun by invaders. That's actually far from the reality. If you've read any sort of Roman history, you'll notice immediately that they're fighting them all the fucking time. Nowadays we think of the Celts being on the fringes of the British Isles, but then you remember they speak a Celtic offshoot down in Brittany, France. That's the only vestige left of the great Celtic empire that spread across the European continent.

Because the Celts aren't from the British Isles. Far from it. Scholars aren't completely certain where they're from — I've seen shit from on the northern coast of the Black Sea to around where modern-day Czech Republic is — but they certainly were invaders. At one point they controlled central Europe, France, and most of Spain. Eventually they pushed into the Italian peninsula, where they rubbed against the Romans, who bought them to their doom. Under Julius Caesar they lost France, during the 100s B.C. the Romans sent legions into Iberia, and eventually even Britain fell. So although we say there was a Celtic population in Britain when the Anglo-Saxons arrived, that's not true: It was a combination of Celts and some earlier, pre-Iron Age peoples we don't know much about due to lack of texts. We just have stuff like Stonehenge to give us a sense of their culture.

Celtic pride is often used to show a firey underdog, whether it was the English conquerors in Ireland or Scotland or the immigrants coming up against the WASP hierarchy, but then you realize at some point the Celts were the ones invading and taking the land; we just don't have the records about it unless if we're dealing with the Romans. And Romans were quick to say that the Celts were a pretty fucking terrifying people. It just reminds me that we all have ancestors who were once oppressed, but simultaneously we all have ancestors who were the oppressors.

^* David Crystal, The Stories of English (New York: Overlook Press, 2004), 3.