The farthest back I think, and I think I've said before, is when I first started playing Lord of the Rings Online when I was getting really into the books. I think it was actually called the "Minstrel" class so I have no idea where I got the name "Bard". I think it was from The Hobbit? I know it was a name of the character that killed Smaug.
I dunno, but I made it up on the spot because I thought it'd be easy to remember because it was so whimsical to me. I'd have used something different if I was going to be using it for so long, but it stuck and it fit the character I made for the game too.
A friend came up with an alternate version I use that's based on a Final Fantasy joke I think, "SpoonyBard".