"Greasy" was a double entendre

It may seem obvious, but I only to put this together after seeing the film - the villain had a penchant for grease of course, but there was a second meaning: A reference to the disco era and the film "Grease" with John Travolta. I think the film specifically mentions John Travolta as a subtle hint to establish this connection. A third meaning is that the Dad was greaseball, or greasy character i.e. the slang word for douchebag. So the joke here is they took the literal meaning of grease and applied it to the horror villain, but they also use two figurative meanings, so the title of the film works on three levels.