Where does “ஜலம்” come from?

ஜலம் (Tamil) comes from Sanskrit जल, from Sanskrit जल् — to be sharp; to be stiff or dull.

ஜலம் (Tamil): water

Definitions

Step	Language	Word	Meaning
1	Sanskrit	जल	stupid, unintelligent, dumb; a stupid man, idiot;...
2	Sanskrit	जल्	to be sharp; to be stiff or dull

ஜலம் — Etymology, Origin & Word History | Etymology Explorer