Where does “ម្រឹត្យុ” come from?

ម្រឹត្យុ (Khmer) comes from Sanskrit मृत्यु, from Sanskrit मृ, from Proto-Indo-Iranian *mar-.

Ancestry of “ម្រឹត្យុ”, step by step

Step	Language	Word	Meaning
1	Sanskrit	मृत्यु	death, dying; Death personified, the god of...
2	Sanskrit	मृ	to die
3	Proto-Indo-Iranian	*mar-	—

ម្រឹត្យុ — Etymology, Origin & Word History | Etymology Explorer