'backbreaker' originates from English as a compound of 'back' and 'breaker', where 'back' meant the rear part of the body and 'break' meant to fracture or destroy.

'backbreaker' developed from the literal phrase 'to break one's back' (used about physical injury). Over time English speakers formed the compound noun 'backbreaker' to describe anything that would figuratively or literally break the back, and later extended the sense to mean 'an extremely arduous task'.

Initially, it referred to something that could literally break the back; over time it evolved to mean 'something extremely strenuous or exhausting' in a figurative sense.