Where does “καμάρᾱ” come from?

καμάρᾱ (Ancient Greek) comes from Proto-Iranian kamarā-, from Proto-Iranian kamárati, from Proto-Indo-Iranian *kmárati, from Proto-Indo-European kh₂em- — to bend, to curve.

καμάρᾱ (Ancient Greek): Anything with an arched cover such as a covered...