Where does “endocrino” come from?

endocrino (Spanish) comes from Latin endocrinus, from Spanish endo-, from Ancient Greek ἔνδον, from Proto-Hellenic éndon, from Proto-Indo-European h₁n̥dóm, from Proto-Indo-European h₁n̥dó, from Proto-Indo-European h₁én — in.

endocrino (Spanish): endocrine; endocrinologist