Carnival is associated with pre-Lent festivities although the celebration itself may have transcended from pagan celebrations heralding Spring renewal and rebirth.  In the Americas, the festivities that you see today are a fusion of many cultural backgrounds from different parts of the world. However, it still finds its association with ancient Roman Catholicism.

The other carnival was a term coined in America in the 1920s and, with a different pronunciation, is associated with a traveling circus.