A balisong, otherwise known as a butterfly knife or a Batangas knife, is a Philippine folding pocket knife with two handles counter-rotating around the tang such that, when closed, the blade is concealed within grooves in the handles. In the hands of a trained user, the knife blade can be brought to bear quickly using one hand. Manipulations, called flipping, are performed for art or amusement.
While the meaning of the term "balisong" is not entirely clear, a popular belief is that it is derived from the Tagalog Language words baling sungay (literally, "broken horn") as the original balisongs were made from carved animal horns. These knives are also referred to as "fan knives" or "click clacks."
The use of the balisong is so popular in the Philippines that an urban legend exists about every Batangueño carrying it everywhere he goes. They are a pocket utility knife used by people of Filipino society. They have also been used to fight duels over matters of honor, although such practices have been discontinued for decades.