True, not particularly horse- related. Just spinning things. A twig blocking the grass mower. It might be interesting to know when the expression was first used.

Quote:
"It gets its common name from the legend that other smaller species of fish could ride on the back of it over great distances."

That's cute. A legend or reality ? A live mackerel has a really splendid multi-colored skin. A friend brought some home from a fishing trip off the coast here. A favorite fish.