Where does “ராசி” come from?

ராசி (Tamil) comes from Sanskrit राशि, from Proto-Indo-Aryan rāśíṣ, from Proto-Indo-Iranian rāćíš, from Proto-Indo-Iranian rać-, from Proto-Indo-European reḱ- — to bind.

Ancestry of “ராசி”, step by step

Step	Language	Word	Meaning
1	Sanskrit	राशि	a heap, mass, pile, group, multitude, quantity,...
2	Proto-Indo-Aryan	rāśíṣ	—
3	Proto-Indo-Iranian	rāćíš	—
4	Proto-Indo-Iranian	rać-	to bind, tie
5	Proto-Indo-European	reḱ-	to bind

Every word from Proto-Indo-European reḱ- →

ராசி — Etymology, Origin & Word History | Etymology Explorer