The term 'Cousins of Mandolins' refers to lutes, which are stringed instruments that have been around since ancient times. Lutes have a long neck and a round body with a flat back, and they are plucked or strummed with the fingers. They are related to mandolins, which are similar in shape but have a shorter neck and are usually strummed with a pick. Both lutes and mandolins are popular instruments in folk and classical music.