From Proto-Khasian *sŋiː, from Proto-Mon-Khmer *t₂ŋiiʔ. Cognate with Khasi sngi, Western Lawa saŋiʔ, Mal ŋeʔ, Semelai tɲi, Mon တ္ၚဲ, Khmer ថ្ងៃ (thngay), Halang ngay, Vietnamese ngày, Pacoh ingay.
sngi