Where does “άκαμπτος” come from?

άκαμπτος (Greek) comes from Ancient Greek ἄκαμπτος, from Ancient Greek ἀ-, from Proto-Hellenic hə-, from Proto-Indo-European sm̥-, from Proto-Indo-European sem- — together, one.

άκαμπτος (Greek): inflexible, rigid; inflexible, immovable,...