This is actually a really good question, I've been doing some searching and according to the internet, Eddie Elguera invented the fakie ollie and Allen Losi invented the ollie to fakie. Other than that, I don't know why it's called fakie. Maybe skating a ramp or pool and approaching the coping to do an air, and you don't air, so you fake it, fake air, fakie. So then you invent ollie to fakie. Then you go out on the street and do an ollie while rolling fakie, fakie ollie. Thus all the fakie tricks are all named backwards. Fakie is short for fake air, I'm guessing.
Something like, (in a stoner's voice), "He's going to air, no he didn't! He did a fake air! He's going fakie! Whoa fakie!"