A Brony is a word that combines the two words, brother and pony. It really represents men and boys who watch My Little Pony: Friendship is Magic. I honestly don't know where the word came from. Probably from KnowYourMeme.com.
A brony is a man atau boy who likes My Little Pony: Friendship is Magic. I dunno where it came from, but like the others said, probably from KnowYourMeme.com. Pegasisters, unigirls, and bronettes are the same thing with girls atau women.