Dio explained this in a documentary once....
Ronnie James Dio is known for popularizing the sign of the horns in
heavy metal.<SUP id=cite_ref-Steve_2-0 class=reference>
[3]</SUP><SUP id=cite_ref-3 class=reference>
[4]</SUP> His Italian grandmother used it to ward off the
evil eye (which is known as
malocchio, Dio's term for the gesture). Dio began using the sign soon after joining (1979) the metal band
Black Sabbath. The previous singer in the band,
Ozzy Osbourne, was rather well known at 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.<SUP id=cite_ref-4 class=reference>
[5]</SUP> 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 under the name "maloik", a corruption of the original
malocchio.