Where does “εκατοντάδα” come from?

εκατοντάδα (Greek) comes from Greek εκατό, from Byzantine Greek ἑκατό, from Ancient Greek ἑκατόν, from Proto-Hellenic hekətón, from Proto-Indo-European ḱm̥tóm, from Proto-Indo-European déḱm̥ — ten.

εκατοντάδα (Greek): group of 100