Aren't those fishermen's taboos matched by some for miners? Not necessarily coal miners, but mineral men? I'm not sure about the pig, but women and priests were a good reason for not going underground. I have a suspicion that we may be dealing with cthonic (?) matters here. Priests are obviously concerned with death. Women with birth and death (as in laying out). And pigs in mythology are beasts of the underworld. Both the sea and the underground are places where workers wouldn't want to call death to mind, for fear he might come.