Simplify the following text for a Grade 8 native English-speaking person.
Original: `` Ring of Fire '' or `` The Ring of Fire '' is a country music song popularized by Johnny Cash and co-written by June Carter ( wife of Johnny Cash ) and Merle Kilgore .
Simplified: `` Ring of Fire '' is a country music song popularized by Johnny Cash and co-written by June Carter and Merle Kilgore .