The banjo is a four-, five- or (occasionally) six- or even more rarely 12-stringed instrument with a thin membrane stretched over a frame or cavity as a resonator, called the head. The membrane, or head, is typically made of plastic, although animal skin is still occasionally but rarely used, and the frame is typically circular. Early forms of the instrument were fashioned by Africans in America, adapted from African instruments of similar design. The banjo is frequently associated with country, folk, Irish traditional and bluegrass music. Historically, the banjo occupied a central place in African American traditional music, before becoming popular in the minstrel shows of the 19th century. The banjo, with the fiddle, is a mainstay of American old-time music. It is also very frequently used in Traditional ("Trad") Jazz. There are several theories concerning the origin of the name banjo. It could have come from the Yoruba word Bami jo, which means "dance for me." It may derive from the Kimbundu word mbanza. Some etymologists believe it comes from a dialectal pronunciation of the Portuguese "bandore" or from an early anglicisation of the Spanish word bandurria, though other research suggests that it may come from a West African term for a bamboo stick formerly used for the instruments neck.