Well, that's a bit embarrassing... But I'm mostly out now so I might as well answer.
I didn't want to use the screen name I use everywhere when I joined here, because I wanted to remain anonymous, and I didn't want people to just google my screen name and find this forum or something.
At the time, I was starting to like someone, who I still like I should add (it's been 6 months now), and at a loss for ideas as to what name to pick, I just used his as inspiration.
Tonberries are a creature from the Final Fantasy series. His identity online wasn't as a Tonberry though, but a Master Tonberry (a more powerful creature). I picked that name based on the fact that I like him, as this was my reason for joining this forum: prior to that I was poly, but not interested in anyone besides my husband. When it changed I felt the need to talk to people and ask for advice.
I'm fairly certain he knows I like him by now, so I'm less freaked out talking about it. Apart from him, I really couldn't care less who finds out I like him, really.