Where does “lut-” come from?

lut- (Proto-Tocharian) comes from Proto-Indo-European h₁lewdʰ- — to grow; people.

Ancestry of “lut-”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	h₁lewdʰ-	to grow; people

lut- — Etymology, Origin & Word History | Etymology Explorer