The Comparative Tables indicate that primitive initial combinations of nasals and voiced stops generally lost their nasal sound (PE19/20). The same rule applied to “Beleriandic” development in Tolkien’s linguistic notes from around 1950 (PE18/103-4). There are a number of examples of this development in The Etymologies (see below).

However, the actual development in the Comparative Tables shows ✶mb > Ilk. b, mb; ✶nd > Ilk. d, nd; ✶ng > Ilk. g, ng. This indicates that while the normal development was to simple stops, in some case the development could be different. There are a number of examples of such alternate development in The Etymologies. The Doriathrin derivatives of the root ᴹ√ÑGOL all show variations beginning with both g- and ng-, while the Doriathrin derivatives ᴹ√ÑGOROTH all begin with ng-. Similarly, ᴹ√MBOTH > Dor. moth, with a simple nasal instead of a simple stop.

All the examples of this variation are Doriathrin and occur before the vowel [o]. There is an example of a Doriathrin noun with ✶[ŋg-] > [g-] before [a], however: ᴹ√ÑGARAM > Dor. garm. Furthermore, there are no examples of this variation for [nd-], whereas ᴹ✶ndorē > Dor. dôr. Therefore the conditions of this variant development may be where [mb-] and [ŋg-] precede the vowel be [o] (and perhaps [u]) and the variation may be limited to the Doriathrin dialect.

In the case of [mb-], it seems the variation leads to the simple nasal [m-]. It may be that ng- is an orthographic representation of the simple velar nasal [ŋ-], so that in both cases the nasal-stop cluster reduced to a simple nasal for the variation.