hole-builder, hole-dweller

> PGmc. Buþla- 'dwelling', which reflects still earlier *bHúh2-tlo-

> <bytla> 'builder'

What the change u > y reflects: different stages of the language
or the derivation 'dwelling' > 'dweller'?

> <hol-bytla> 'hole-builder' was Tolkien's own
> "etymology" of <hobbit>, "a word that might well be a worn-down form of
> holbytla, if the name had occurred in our ancient language".

E. <hole> < Gmc. <xulaz>, what would be the PIE form?
<k^ol-o-s>? Zero grade <k^l-o-s>?
And what form of the compound can be expected:
<k^ol-bHuh2-tlo-s>, <k^ol-o-bHuh2-tlo-s>, or maybe <k^ol-i-bHuh2-tlo-s>?

P.A.