I shall now proceed to paste stuff from my profile.
One night, in mid April 2012, my sister, cousin and I were all hopped up on chocolate and caffeinated soda, making fun of the generation of MLP we all grew up on. My cousin brought up the seemingly hilarious idea to watch an episode for a nice long laugh. We did, but before we got more than a few minutes into it, a related video had something that caught our eyes. A well drawn pony? Was it possible? MLP got better animation? We unanimously decided to watch the episode Applebuck Season. I personally was amazed by the animation. I had never before seen a little kid's show with such wonderful story boarding, character build up, and design. (I guess I kind of decided to also explain how I became a brony xD)
Flash forward two months.
We were all hopped up on sugar again, after we had all joined the Forums. I was thinking about changing my name. My cousin later came up with this question; If you had to name yourself after something a pony owned, what would you name yourself? I loved Octavia, so I answered Octavia's Cello. My sister said Party Cannon.
Flash forward another while. Not sure how long this stretch was.
I saw Pinkazoid's little Zoid bandwagon thingy. I thought it was silly, and it was annoying at first. I can quote myself; "I will never join the Zoid bandwagon. It's stupid." Well, a short while later, I changed my mind, and changed my name to Octavia's Cellozoid.
TL; DR?
It came from a joke,