I was mistaken, but not about Dio coining the horns.
Heavy metal culture
Ronnie James Dio was known for popularizing the sign of the horns in
heavy metal. He claimed his Catholic Italian grandmother used it to ward off the
evil eye (which is known in Italy as
malocchio). Dio began using the sign soon after joining the metal band
Black Sabbath in 1979. The previous singer in the band,
Ozzy Osbourne, was rather well known for using the
"peace" sign at concerts, raising the index and middle finger in the form of a V. Dio, in an attempt to connect with the fans, wanted to similarly use a hand gesture. However, not wanting to copy Osbourne, he chose to use the sign his grandmother always made. The horns became famous in metal concerts very soon after Black Sabbath's first tour with Dio. The sign would later be appropriated by heavy metal fans.
en.wikipedia.org