Is hyle: possibly related to Latin selva?
If so, I suppose the link would require metathesis from something like
*sewla
As I remember, both words have been ascribed to non-IE substrate in various
articles

> > Incidentally, what's Greek ul-?
>
> I thought Greek also had words with ul-
> having to do with arm like Latin.

All the Greek words in the abridged Scott and Liddell starting ul- (or
rather hul-) are to do with wood (e.g. hyle:) or the barking of a dog.