Can anyone say how these two words, so similar in sound though not meaning, developed?

napier (NAY-pee-uhr) noun

One in charge of table linen in a royal household.

[Apparently from Anglo-Norman nape (tablecloth).] and

nape
"back of the neck," c.1300, of unknown origin, perhaps from O.Fr. hanap "a goblet," in reference to the hollow at the base of the skull.
Online Etymology Dictionary