I have had three usernames over the years. Arilotorchie, Skull_Kap, and Willabye.
Arilotorchie: I didn't start playing Minecraft on the computer until late 2013, but my cousins and I had played together on Pocket Edition dating back to before they had chests and beds (Update Alpha 0.4.0). On pocket edition, your gamer tag was by default names Steve and you had to go into setting and just change it. Well, I couldn't come up with a name so one of my cousins said, "Just do something that sounds weird, like Arilotorchie or something." And that's what I did.
Skull_Kap: My oldest cousin had moved on to the PC version to play on servers, and as a flock of sheep the rest of us kids did too. With buying an account I had decided that Arilotorchie was too unique of a name. I had played the computer version on other people accounts, and I always thought it was funny to put a Steve head on top of Steve's head. With a quick change of words I was using a Skull as a Cap, sadly SkullCap and Skull_Cap were taken so I switched out for the K.
Willabye: I changed my username for the first time in years because I felt like I outgrew the name Skull_Kap. Almost every game I played had Skull_Kap as the tag, but one game called Town of Salem didn't allow underscores and the name SkullKap was taken. If you don't know what Town of Salem is, play it is fun, but it is like the party game Mafia. In playing you have to convince people of true or false information depending on if you are good or bad. This started as me using the name Ali-bye. There is also a part of the game that when you die, a Will that you write out over the course of the game is shown, this morphed into Willabye.