Comment by WalterBright

Back at Caltech in the 1970s, every student got a free account on the PDP10. The account username consisted of 3 letters, and Caltech would assign them by the first letter of their first name, middle name, and last name.

Enter Tim Rentsh. He didn't have a middle name, so Caltech asked what letter would he prefer, so he said X.

TXR

That became his nickname, and stuck so hard he legally changed his name to Tim X Rentsh.

Eat your heart out, Elon! :-)