Since the 1,200 baud days, I had an IT related username that also included part of my company name. An overly curious, possibly malicious tech at a customer site in Michigan doxxed me and posted pictures from my private (but not secure enough) FTP site as well as details of my personal life to tech boards that we were both members of, and he shared what he found with his company, who deemed them inappropriate and decided they didn't want to do business with someone who would be in pictures such as these. This was a little before Y2K. Ultimately, the damage with the customer was repaired, and the tech was let go, but I had to change my username everywhere. At the time, I was, and had been riding and road-racing several generations of Honda CBR600 motorcycles from the early 90s to the mid 00s (with an occasional GSX-R 750 thrown in for good measure). The night before I had to delete and recreate my accounts, one of my rider friends told me I danced like a worm - probably as an insult. I've been CBRworm ever since. Only a handful of people know me by both usernames, and only a handful of people in my circle of friends know my current username. If I had to recreate an account later for some reason, I used CBR.worm.
It is beyond time for me to change my username again, but I now have a legacy of almost 20 years on some board with this name and I hate to have to rebuild my online personality.