Where does “सूक्ष्म” come from?

सूक्ष्म (Sanskrit) comes from Sanskrit सुक्ष्म, from Sanskrit सु-, from Proto-Indo-Aryan Hsu-, from Proto-Indo-Iranian Hsu-, from Proto-Indo-European h₁su-, from Proto-Indo-European h₁wes- — good; to be cheerful, happy; to eat, to feast.

सूक्ष्म (Sanskrit): acute, subtle, keen; nice, exact, precise;...