In Mediterranian and Indian traditional cultures, this gesture was believed to give supernatural  protection against devils, evil eye and other sorts of evil. 

In the 20th century the sign of horns has got a new life thanks to Ronnie James Dio, who began using it at the concerts soon after joining Black Sabbath band, and thus made it one of the symbols of the Heavy Metal culture. Nowadays it is also known as the Metal fork or Devil's horns.