AQ. [z] assimilated to following [m], [n]; [zm|zn] > [mm|nn]
After the voicing of s to z, the combinations zn, zm became nn, mm. This change is mentioned in both the Outline of Phonetic Development [OP1] from the 1930s and the Outline of Phonology [OP2] from the 1950s:
The earliest of these voicings, possibly already in CE, or at least AQ, was in sm, sn > zm, zn. The product of these in PQ was mm, nn. When later but before the general medial voicing of s the suffixes m, n were re-added to voiceless [s] the nasal was probably unvoiced and sm, sn > sw, st [per note #109 Tolkien wrote an “X” the margin next to this and then “zm, nn”]. But cases are rare, and may be usually explained by suffix-alternation (OP1: PE19/49).
The change of sm, sn > zm, zn was the earliest. Here the phonetic change was > mm, nn. These were preserved in PQ and Noldorin TQ. In Ñ. after the change of z > r, in that dialect the etymological or grammatical relations of r to mb/nd became obscure and rm, rn were sometimes produced by re-formation as in √LAS “listen”, AQ lammo “listener” (spy or scout), Ñ larmo (OP2: PE19/101).
It is not entirely clear when zn, zm became nn, mm, but it must have been before [z] became [r]. The example AQ. lammo above indicates the sound change occurred in AQ; this word is also the best example of zm > mm. The best example of zn > nn is ᴹ✶besnō > ᴹQ. venno “husband” in The Etymologies (Ety/BES).
Conceptual Development: In the Qenyaqetsa from the 1910s Tolkien said that s before n, m ultimately became rm, rn (PE12/19). Examples include:
The small number of examples makes it difficult to determine when Tolkien adopted the rules described in OP1 and OP2.
References ✧ PE19/82, 101
|Before||03800||Q. [z] became [r]|
Phonetic Rule Elements
||✧ PE19/82 (zm > mm); PE19/101 (zm > mm)|
||✧ PE19/82 (zn > nn); PE19/101 (zn > nn)|
Phonetic Rule Examples
|lazmo > lammo||zm > mm||√LAS > AQ. lammo||✧ PE19/101|