The term 'Sumatra SWINGER' is a combination of two words: 'Sumatra' and 'SWINGER'. Sumatra is an Indonesian island located in the Indian Ocean, and is the sixth largest island in the world. SWINGER is a term used to describe someone who engages in recreational sexual activities with multiple partners. Therefore, the term 'Sumatra SWINGER' refers to someone who engages in recreational sexual activities with multiple partners on the Indonesian island of Sumatra.