From Proto-Vietic *p-soːs (“lungs”), from Proto-Mon-Khmer. In the more innovative Vietic languages, *-s- debuccalized into *-h-, then developed regularly to the current Vietnamese form. In this particular case, this *-s- > *-h- shift might also have been influenced by sound symbolism. Cognate with Tho pʰɔːl⁵, Thavung pasuh¹, Pacoh xóh, Bahnar dơsoh, Mon ကသံ (kəsɔˀ).
Medial *-s- has the tendency to debuccalize among Austroasiatic languages, compare Proto-Katuic *psaj, *phaj (“otter”) (cognate with Proto-Vietic *p-seːʔ), where conservative *-s- and innovative *-h- can both be reconstructed; the other Austroasiatic languages have innovative *-h-, e.g. Khmer ភេ (phei). Compare also Proto-Katuic *ksaj (“moon”) vs. Proto-Bahnaric *khaj (“moon”), Khmer ខែ (khae), Proto-Vietic *saːmʔ (“eight”) vs. Proto-Bahnaric *t(n)haːm (“eight”).
Unrelated genetically to Chinese 肺 (OC *pʰo-s) (B-S) (SV: phế), although there might had been contamination.
(classifier lá) phổi • (𦟊, 配, 𦡮)