[Oshkalaboomboom]

I agree. I understand that there was a crowd photo where everyone was giving the “devil” hand sign.

The "Devil sign" was popularized by Ronnie James Dio when he took over as the lead singer for Black Sabbath after the departure of Ozzy Osbourne. Ozzy used to flash a peace sign during concerts and Ronnie wanted to keep some continuity in the show without it looking like he was just trying to be an Osbourne clone. He borrowed the hand sign from his Italian Grandmother where using it to ward off Malocchio, the evil eye, was commonly used. So it became popular basically because it was easy to do and looked cool to the audience. The only connection to Satan was made by people who were totally clueless but wanted to find a way to disparage a type of music they didn't like.

[Blue Jays]

Ronnie James Dio was also one of the nicest people ever to hold a microphone. Complete gentleman and legendary vocalist.

[Viking2002]

A variation of that story is, Ozzy did, in fact, originate it, and Ace Frehley of KISS picked up on it and made it even more popular. Ozzy admonished him not to use it due to all of the flak he was getting, but Ace kept it up. Then again, that's Ace's side of the story, and he's spent most of the last 40-odd years either too drunk or too stoned to unzip his fly when he pees, so take that as you will. LOL