Others' Island (spoilers all books incl RWC)

[Nuytsia]

In the RotE books themselves, the only real references to nails that I can think of is Fitz and Fool nibbling on the corner of their thumbnails now and then; Thymara's claws instead of nails and Beloved's loss of them during the Pale Woman's torturing of him....hmm...could there be something even in that?! I don't think so BUT if there couldn't be a link to Kitten-Thick and the drowned kittens of Kennit's, there's no reason there could be a link with Kennit's nails and Fool?

Isn't it the case that if your fingernails are completely torn out they don't grow back at all?

The only reference to fingernails I can think of in other books is in Hogfather by Terry Pratchett. The reference is primarily to the teeth collected by the tooth fairy, but I am fairly certain at one point they are talking about why someone would want to steal children's teeth and they say something like body parts such as teeth, fingernails and hair can give you power over the person (who they came from). Something about it being very old magic.
Also like voodoo I guess!