Boise (pronounced boy-see) is the capital of Idaho—and the only U.S. state capital named after the river it sits on.
French-Canadian trappers called the tree-lined river "La rivière boisée" ("the wooded river"). The name migrated to the fort (1834), then the city (1863), then the territory/state.
If "bouncy" means fun-to-say: Honolulu (HI), Santa Fe (NM), Baton Rouge (LA), Little Rock (AR), Oklahoma City (OK). But only Boise shares its name with its river.