The term 'ukulele cousin' refers to the banjo, a five-letter stringed instrument that is related to the ukulele. The banjo is a four- or five-stringed instrument with a circular body and a long neck. It is typically played with a pick or the fingers and is known for its bright, twangy sound. The banjo has its roots in African-American music and was popularized in the United States during the 19th century. It is now a popular instrument in many genres of music, including bluegrass, folk, country, and jazz.