The term 'Island Guitar' refers to two different instruments: the uke (3 letters) and the ukulele (7 letters). The uke is a small, four-stringed instrument that originated in Hawaii and is often associated with traditional Hawaiian music. The ukulele is a larger version of the uke and is also associated with Hawaiian music, but it has become popular in other genres as well. Both instruments are commonly used in island music, hence the name 'Island Guitar'.