'atony' originates from Greek, specifically the element 'a-' + 'tonos' (often seen in the form 'atonia'), where 'a-' meant 'not' and 'tonos' meant 'tension' or 'stretching (tone)'.

'atony' entered English via Late Latin/medical Latin 'atonia' (from Greek 'atonos'/'atonia') and was adopted into English medical vocabulary in the 17th–18th centuries as 'atony'.

Initially, it meant 'absence or lack of tension/tone' in Greek medical usage; over time it has retained this core meaning and is used in modern English to denote loss of normal muscle or organ tone.