I go back to Air Warrior version 1.0, about 23 years ago. At first there were no handles; they assigned plane numbers when you signed up. I was plane number 715. Much later they decided to add handles and, being creatively challenged, I just used my plane number. I was the only player allowed to use my plane number as my handle, so I am the original "annoying numbers guy".
When I moved from AW (to Confirmed Kill, then to Warbirds and then) to Aces High, I chose 715 as my handle. When Aces High came out of beta they had everyone pick a new handle (I don't remember why) so I became 715A. Years later, in frustration, I quit. When I restarted, I became 715B.