Where does “ក្រុង៑” come from?

ក្រុង៑ (Old Khmer) comes from Proto-Mon-Khmer kruŋ — to confine.

Ancestry of “ក្រុង៑”, step by step

Step	Language	Word	Meaning
1	Proto-Mon-Khmer	kruŋ	to confine

ក្រុង៑ — Etymology, Origin & Word History | Etymology Explorer