Heavy metal fans are familiar with the so-called "sign of the horns" or "devil horns," made by extending the index finger and pinky.
But in many European and South American countries, including Italy, Spain, Greece, Brazil, Argentina, and Colombia, the gesture has a more obscene meaning.
There, it's used to mock cuckolds — husbands whose wives are unfaithful. The connection is obvious to people from those countries: the word for "cuckold" in Italian, Spanish, and Greek is the same word for "horned."