Merry-go-round rhymes with:
background, battleground, campground, fairground, foreground, playground, runaround, underground, background, battleground, campground, earthbound, eastbound, electrosound, fairground, foreground, foxhound, greyhound, hidebound, homebound, horehound, outbound, playground, runaround, snowbound, southbound, spellbound, turnaround, underground, westbound