Generally speaking --
Christianity: Horns = Devil
Christianity: Devil= Big, scary evil, beastie (generally advocates sex as sin)

Pagan: Horns= Horned God (generally advocates sex as celebration)
Pagan: Devil= ????

Smush them together... and, Poof! You've got that cute little dude with the cool name.

Early Christianity tended to demonize a LOT of things, not just pagan gods. It also had whimsical interpretations... when it didn't outright make stuff up. And Anton LaVey had whimsical interpretations... when he didn't outright make stuff up. Still along with the bits of badness that some people take from them, there is merit to christianity, paganism, satanism... so on and so forth.