From Proto-Vietic *koh (“throat; neck”), possibly from Proto-Mon-Khmer *kɔʔ (“neck”); cognates include Khmer ក (kâ), Bahnar hơko, Mon ကံ. Compare Proto-Tai *ɣo:ᴬ.
Sino-Vietnamese word from 古
From cô. Adding the hỏi tone is a means to form a third person singular pronoun in Southern dialects.