Yes, pretty recently Frommer announced that the "ultimate, final" is tor, and "shadow" is uk, just as in Toruk.

To make a "rain-shadow" name...you could use something like...Tompauk (literal), tomuk is also possible, but it loses bit of it's root...

What about tompuk? tomp'uk? tom'uk? Or even (after trying to decipher the rules) Uk'tompa?
That last one would translate as Shadow of Rain which would work as well. Stabbing in the dark with a dull mind.

Well... Firstly something of rules of grammar.
Tompuk wouldn't work as 2 consonants (m and p) would be next to each other, creating different syllabylles. So the word wouldn't be tomp-uk, but rather tom-puk (and puk means "book")
Tomp'uk and Tom'uk... well the ' isn't just there to make things more fancy:xD:, it's a letter basically and since none of the words include it in their normal form I doubt it would appear here either.
Uk'tompa or Uktompa wouldn't work also due to the rules mentioned above...
(oh, and p' and k' would actually be written as px and kx ;))
That much of theory.

However!!... those are names only, so I bet it wouldn't be such a huge deal if there are few grammatical errors....