Reconstruction:Proto-Austroasiatic/tNɕaːm

• Proto-Austroasiatic: *tNɕaːm (Sidwell, 2024, #AA338)
• Proto-Mon-Khmer: *t₁haam (Shorto, 2006, #1431.A)

The Pre-Proto-Khmuic form was something like *thaːm, with typical debuccalization of the medial sibilant (reconstructed here as *-ɕ- by Sidwell (2024)). Due to Proto-Khmuic's constraint against *Ch- onsets, medial *-h- was then lost; compare the triplet Khmu [Cuang] biʔ ("full, sated") (loss of debuccazed *-h-) vs. Bahnar phĭ (preservation of debuccazed *-h-) vs. Eastern Bru pasâi (preservation of the original sibilant). Bahnaric similarly also shows debuccalization. Pakanic and Vietic, on the other hand, preserved the sibilant but dropped the presyllable. Thus, Vietnamese tám and Khmu [Cuang] taːm, despite being cognates, contain onsets of different origins: Vietnamese /t/ reflected what reconstructed as *-ɕ- here, while Khmu /t/ reflected *t-.

Old Mon was conservative in neither showing debuccalization nor loss of the presyllable.

*tNɕaːm

1. eight

• Proto-Bahnaric: *t(n)haːm (Sidwell, 2011) (see there for further descendants)
• Proto-Khmuic: *taːm (Sidwell, 2013) (see there for further descendants)
• Monic:
  • Old Mon: diñcām ~ dincām
    • Middle Mon: dacām ~ dacāṁm
      • Mon: ၈
  • Nyah Kur: ɲcaam
• Proto-Munda: *tam (Rau, 2019) (see there for further descendants)
• Proto-Pakanic: *saːmʔ (Hsiu, 2016) (see there for further descendants)
  • Bolyu: saːm⁵³
• Palaungic:
  • Danau: ʦɑn⁴
• Proto-Vietic: *saːmʔ (Ferlus, 2007) (see there for further descendants)
  • Vietnamese: tám

• Shorto, Harry (2006) Sidwell, Paul, Doug Cooper and Christian Bauer, editors, A Mon-Khmer Comparative Dictionary, Canberra: Australian National University. Pacific Linguistics, →ISBN
• Sidwell, Paul (2024) “500 Proto Austroasiatic Etyma: Version 1.0”, in Journal of the Southeast Asian Linguistics Society‎^[1], volume 17, number 1, pages i–xxxiii