A male spider ought to be called "
Helob"
(Inspired by Maggie Honeybite's hilarious fanfiction "Spiders in the Mist" whose protagonists are called Helob and Morliant.)
I personally wouldn't fancy giving any noble Elven or human names to pets.
Huan for a dog would be very appropriate, though, or think of all the great names for horses: Arod, Hasufel, Shadowfax, Roheryn, Firefoot, or Stybba for a pony.
As for naming children - well, it's too great a responsability, I think, to saddle them with Middle-Earth names for life that might be the subject of ridicule later...
Our sailboat already got a name before my Tolkien-obsession ("Guinevere", btw) or else there would be a number of great names to choose from (from U.T mostly)! At least I have named our dinghi "Entulessė" (meaning "return")