'backaching' originates from English, specifically the word 'backache', where 'back' meant 'the rear part of the body' and 'ache' meant 'pain'.

'backaching' developed from Middle English compounds such as 'back-ake' (back + ake/ache); 'ache' itself goes back to Old English 'æce' (later 'ache'), and the modern form 'backache' produced adjectival/participial forms like 'backaching'.

Initially it referred simply to 'pain in the back'; over time the basic sense has remained stable, with related adjectival and participial forms used to describe the pain or the state of suffering it.