Just as a point of interest: the most important American "carnival," in the traditional sense, was undoubtedly the New Orleans Mardi Gras. By the mid-1890s "traveling carnival companies" began to appear. These were itinerant outfits equipped with acrobats, clowns, jugglers, a few animals, and so forth that would essentially put on a "carnival" (a completely secular outdoor entertainment) in rural areas. They were essentially small traveling circuses.
It didn't take long for "carnival" to expand its meaning to include a "carnival company" itself ("ran away to join a carnival"), not just the old idea of a religious and later secular street celebration.
How long it took the new usage to reach the British Isles, I can't say.