i know you were away from tumblr for a long while lol, can't remember the post off the top of my head, but "blorbo" originates from a joke post about how people tag posts with like, (insert character) from some show they like. naturally, people who saw it went crazy with it and it's become slang for someone's favorite character.
Ah, thanks bestie, I was thinking it was something like that, but wasn't sure