Reconstruction:Proto-Vietic/b-laŋ

This Viet-Muong etymon is often compared with Austronesian *bulaN 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 *-ŋ, 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, Chut [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 -n 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 ă-a, instead of a-aː), while the Viet-Muong forms have short vowel.

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

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

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

*b-laŋ

1. moon

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

      → Northern Vietnamese: trăng