From Proto-Mon-Khmer *kaʔ (“fish”). Earlier *k(ʰ)- was lost in inherited words and early loans, compare ʔɛːk⁷ (“guest”), ʔaː³ (“dry”), vaːŋ¹ (“wide”), ʔɛːp⁷ (“narrow”), ʔeːŋ⁶ (“hand”), ʔan¹ (“to bite”).
ʔaː¹
