Where does “atony” come from?

Atony comes from New Latin atonia, from Ancient Greek ἀτονία, composed of the prefix ἀ- and τείνω, ultimately derived from Proto-Indo-European roots meaning "not" and "to stretch."

atony (English): Lack of muscle tone; flaccidity or atonia

Definitions

Lack of muscle tone; flaccidity or atonia

Ancestry of “atony”, step by step

Step	Language	Word	Meaning
1	New Latin	atonia	—
2	Ancient Greek	ἀτονία	languor
3	Ancient Greek	ἄτονος	languid
4	Ancient Greek	ἀ-	The alpha privativum, used to make words that...
5	Proto-Hellenic	hə-	same; together
6	Proto-Indo-European	sm̥-	one; with, together
7	Proto-Indo-European	sem-	together, one

Every word from Proto-Indo-European sem- →Every word from Ancient Greek ἀ- →Every word from Proto-Indo-European sm̥- →