Is 'if you step on a crack you will break your mother's back' a superstition?

It has been around for centuries and will be around for many more. It began as part of a jump rope rhyme. When little girls jump rope they come up with nonsense sayings. They do not make sense. They simply maintain rhythm. "Fudge, Fudge, call the judge." "Postman, Postman, do your duty." "Here comes Jane the American beauty." "Step on a crack, you break your mommies back." They will never be great poetry. They go from generation to generation.