"Ten-gallon" is a slang term for the stereotypical tall, wide-brimmed cowboy hat. There are several theories of the term's origin - one of the more common is that it's a corruption of the Spanish term "tan galán," or "very fine." There are other theories, which I think are also the result of English-Spanish crossover terms.
Anatomically speaking, though, a lobster's claws are still considered legs. They actually have claws on three of their five pairs of legs; the front pair is just much larger than the other two. (I do think the question should accept "limbs," though.)