Harley Clark had no idea what he was doing when, as head cheerleader at the University of Texas at Austin, he introduced a hand gesture to his fellow students at a rally. Clark said the new gesture was now the official sign for the Texas Longhorns football team, to be used whenever they played. The sign, made by raising the index and pinkie fingers while holding the rest down, was thought up by a classmate, and was supposed to resemble the school's horned mascot. After the rally, Clark was chewed out by an administrator, who said he had no authority to make such a proclamation. Besides, the gesture had a terrible meaning in Italy [source: Nicar].
But the "Hook 'em Horns" sign was immediately embraced by Longhorns fans, and a decade later by American rockers, who used it to encourage fans to party on. Not a big deal in America, of course, but in countries such as Italy and Spain, as well as in Brazil, Colombia and some Baltic nations, the sign (known as a corna or cornuto) is an offensive gesture letting a man that, "Hey, your wife's a whore." The "bull horn" insult dates back at least 2,500 years — bulls used to be castrated to make them calmer [source: Telegraph].
The gesture is also used as a satanic salute. This became problematic for President George W. Bush when, in 2005, he flashed the Hook 'em Horns sign at his second inauguration. Some Nordic newspapers proclaimed he was hailing Satan [source: Link]. In 1985, use of the gesture also caused five Americans to be arrested. The group, visiting Italy, was celebrating a major Longhorns victory by dancing with "devil horns" near the Vatican [source: Google Books].