Reconstruction:Proto-Vietic/b-laŋ

Etymology
This Viet-Muong etymon is often compared with Austronesian and the likely related Kra-Dai terms; however, in spite of Ferlus' reconstruction, none of the modern reflexes indicate that the labial element was voiced (the tones in the languages belong to upper register, signifying a voiceless presyllable), and they uniformly have final, which does not match with either Austronesian (PA with lateral coda, PMP and its reflexes with alveolar nasal) nor Kra-Dai forms (with alveolar nasal coda).

On the other hand, 🇨🇬 [Mày] pula̤n² ~ pala̤n² (Babaev & Samarina, 2018) (as well as its close cognate in Rục) is a more obvious loan, with lower register tone indicating earlier voiced presyllable, and a coda. Note that this Viet-Muong etymon and Chứt forms can not be immediate cognates (if they are even related at all); beside the aforementioned differences, the vowel of the Chứt forms is long ((Babaev & Samarina, 2018) indicates vowel length in Mày as, instead of ), while the Viet-Muong forms have short vowel.

In short, the Viet-Muong forms listed here point to (voiceless presyllable, short vowel, velar nasal final), while the Chứt forms point to  (voiced presyllable, long vowel, alveolar nasal final).

Considering all the above, it is most likely that this Viet-Muong item is simply a false cognate with the Austronesian and Kra-Dai terms; the words in Rục and Mày (< ), on the other hand, are straightforward loanwords from Austronesian, most likely from Chamic specifically. The reconstructed by Ferlus (2007) with voiced presyllable is most likely a ghost.

Among Vietic languages, there is another etymon for "moon", gave rise to [Cuối Chăm] plɔŋ²,  palɔ̂ːŋ, that is also unrelated to both of etymons mentioned above in spite of superficial similar shape. Lastly, ⁿrah is of unknown origin.

Noun

 * 1) moon

Descendants

 * Viet-Muong: *p-laŋ (Ferlus reconstructed but there is no internal support for voiced presyllable)
 * Muong:
 * Bi:
 * Proto-Vietnamese:
 * Northern Middle Vietnamese: (de Rhodes, 1651)
 * Inland Northern Vietnamese:
 * Coastal Northern Vietnamese:
 * North Central Vietnamese:
 * Southern Vietnamese: