I was 12.
Let's leave it at that.
the story behind your name is AMAZING though lol..
well, my names aren't very original, but i have a lot ~_~ people keep asking what they are, so...
when i was twelve or so, i watched a lot of anime, and one of the anime i liked (angelic layer) had a character named misaki. in the series she got a nickname, 'misaki-chi', and when asked for her name in a tournament, she said she was misaki-chi instead of her full name, which was incredibly awkward but endearing. i began using it on other forums and sites, and when i signed up, i just wanted to correct the site's grammar and fade back into oblivion, so it didn't matter to me what i signed up with. unfortunately the name is old and i didn't really want to stick with it, but for ages i resisted having my name changed because it's what i signed up with, i assumed jumpluff was taken, and it's what i was known by on the forums, although tbh i mostly post in c&c and everyone there knows me as shiki / jumpluff anyway.
shiki misaki is a video game character. part of the reason i picked it is to match with 'misaki-chi'. i lost the pass to my misaki-chi shoddy alt, so i made shiki misaki as a testing alt, and stuck with it. there have actually been multiple users surprised to learn shiki misaki isn't actually my name!
jumpluff is what i'm most known by because i use it on IRC, and i recently had my forum username changed to it to avoid confusion. in the past, i was confused with users like jumpy fluff, much to aldaron's chagrin (so much he didn't like me at first, but we're cool now etc.!) i like the pokémon jumpluff and i like the look of the word (the low tail of j and p combined with the stems of l and ff) as well as its sound, so when i began lurking around smogon IRC, i just used it.