My legal first name is James, though I’ve never really gone by James. Where I grew up, Jas. was the short-form of James (instead of Jim) and children mostly only went by their family names at school. When I moved back to the United States at thirteen years-old, I’d sign my name “Jas. Powell” and a number of people had difficulty with my cursive writing of the letter S, so it stuck as “Jaz” or “Jas”, which is the formal diminutive form of James. I’ve kept it and adopted Jas. as my first name ever since. Not a very interesting story, but there you go.