When I joined there weren't a lot of members so a lot of basic one-word usernames were available. I was searching around for something that sounded good and was unrelated to any other online identities, when an advert for Admiral insurance played on the telly.
It's simple, has a nice ring to it and is also a common enough word that it would be pointless to search for on google if someone were to try to dox me (I hope they wouldn't though- I'm really boring). If I had to change it, I would give it a capital letter.