'bareback' originates from English, specifically the words 'bare' and 'back', where 'bare' meant 'uncovered' and 'back' referred to the 'back' (as in the horse's back).

'bareback' developed as a compound of 'bare' (Old English 'bær'/'bær(e)') and 'back' (Old English 'bæc') in post-medieval English to describe riding on a horse's bare back; the compound usage is recorded from the 18th–19th century and has since maintained its literal sense, later gaining figurative/colloquial sexual meaning.

Initially, it meant 'on the bare back (of an animal)', but over time it retained that primary meaning and also acquired the modern colloquial meaning of 'without protection' in a sexual context.