Comes from Angul, a district in Schleswig, North Germany. Some of the local tribe moved to, and settled in, eastern parts of England - what is now called East Anglia.

There is a tale that I have heard that when the Romans first came to Britain they saw these fair haired people and thought they looked liked like angels which gave rise to the name; but that sounds to me like a Victorian invention or maybe William Blake (it's a bit Jerusalem-ish).