Long, LONG story...
Back when I used to watch Cartoon Network, one of the cartoons I followed was Ed, Edd n Eddy. For some reason, I always remembered Rolf (one of the characters) referring to Ed as 'Ed boy' (he just had the sort of voice I find hard to forget ).
For some of my online/gaming accounts, I just refer to myself as ED (because it's the shortened, first two-letter version of my real first name which I'm admittedly not a fan of, as well as the initials of my first and last name). I think, though, that I stuck with it for a while after I realised how very few letters they offered for player names in Super Smash Bros Brawl. 'ED' fitted in, plus it made sense for me.
Later on, though, probably when I made my FanFiction account, I couldn't use ED as a username since it was already taken. I ended up taking ED_Boi instead, which developed into Edwardo_Boi once my cousin started to call me Edwardo a lot. On here, calling myself Edwardo_Boi doesn't make as much sense, bearing in mind 'boy' is not the correct term in the ponyverse (plus, Edwardo_Foal just doesn't have the same ring to it ). 'Brony' seemed the best substitute, so Edwardo_Brony it was.
...
Yes.