Where does “kilohercio” come from?

kilohercio (Spanish) comes from Spanish kilo-, from French kilo-, from Ancient Greek χίλιοι, from Proto-Hellenic *kʰehliyoi, from Proto-Indo-European ǵʰéslom, from Proto-Indo-European sm̥-, from Proto-Indo-European sem- — together, one.

kilohercio (Spanish): kilohertz