In the early days of the web, many people used America Online as their first ISP, including me. Even then, signing up meant creating a unique username. I must have tried 10 or 12 names, all of which were rejected as having already been taken. Finally, in frustration, I used the name of a then-popular steak house, substituting ‘z’ for ‘s’ where ever it appeared. To be sure of its uniqueness, I doubled each ‘z’. It worked and I’ve continued using it for the last 35 years.
My former startup, wprapido.com . I had a previous YN username where I forgot the password. Applied to YCombinator and needed a username. Stayed with it. Sold the underlying tech behind WPRapido, but retained its identity (domain, many usernames all over, etc.) and even had a Ltd. company that I used for it till like 6 months ago
A pretty boring one: My first name with anglicised umlaut in addition to both middle and last initial of my full name.<p>I'm not exactly sure where I first used it but I've been doing so consistently for several years now. It even is the domain name for my business.
Oh, this will probably make me sound way older than I actually am.<p>Still, it's a shortened version of the username I used for Lycos Mail about two decades ago that I've stuck with ever since.
I had started (and then dropped rather quickly) the anime Bungo Stray Dogs, whose characters are named after classic Japanese authors. The main character of the show is named after Atsushi Nakajima.