Where does “t-kuːlʔ” come from?

t-kuːlʔ (Proto-Vietic) comes from Proto-Mon-Khmer -kuul.

Ancestry of “t-kuːlʔ”, step by step

Step	Language	Word	Meaning
1	Proto-Mon-Khmer	-kuul	—

t-kuːlʔ — Etymology, Origin & Word History | Etymology Explorer