VT 46:16, entry SUD- lists the N. words _thund, thonn; thonnas_ (first
written _sunn, sonnas_).
The -nd/-nn variation often occurs in the _Etymologies_ (e.g. _thand,
thann_, VT 46:16) and primitive *u generally yields /o/ in Noldorin.
Therefore, are the -u- read in _thund_ and _sunn_ really certain in
the manuscript, or could they possibly be malformed -o-?
From the few facsimile pages of Tolkien's texts we have, I have the
impression that Tolkien's -o-, when written quickly (esp. before -n),
are sometimes not always fully closed on top (for instance, this seems
to be the case for the final -o- in _Angalagon_ and _ono- on the VT
46:5 facsimile -- unless this is to be ascribed to an artefact of the
printed reproduction or even to my poor sight. I certainly don't claim
to have any experience deciphering Tolkien's hand-writing!)
Of course, S. _thond_ "root" is later attested in _Morthond_
"Blackroot" (e.g. LR app. E).
[Yes, the form is very clearly written as _thund_; likewise, the parallel deleted form _sunn_ is very clearly written as such. A fact not noted in the A&C is that this _sunn_ itself overwrites earlier _sonn_, which reinforces the deliberateness of the _u_ in both forms. CFH]