From Wikipedia:
Ronnie James Dio (born Ronald James Padavona, July 10, 1942, Portsmouth, New Hampshire) is a heavy metal vocalist who has performed with Black Sabbath, Ritchie Blackmore's Rainbow, and his own band Dio. Other musical projects include the collective fundraiser Hear 'n Aid and his band immediately before Rainbow, Elf. He is renowned for his consistently powerful voice and for popularizing the 'horns' hand gesture in heavy metal culture (formed by closing the thumb over the middle and ring fingers, while having the index and little-finger extended). Ronnie said that his grandmother used to make the hand gesture to ward off the evil eye.