This goes back a LOOOOOONG way even in Hollywood.

A couple of weeks ago I was watching the old John Barrymore flick Svengali, about an evil musician who uses mind control/hypnosis over a young singer. I think it's from 1933 and very well done for its time. I'd seen it before but this time I was surprised to note Barrymore throwing the DEVIL'S HORNS sign a couple of times. I assume he was doing this as the character Svengali (as it is done in character towards appropriate people he is hexing) rather than sneaking it in as they do now.

But he knew about this shit even then and there it is, in this old movie.