'muscle-building' originates from the combination of 'muscle' and 'building', where 'muscle' refers to the tissues in the body that can contract and 'building' refers to the process of constructing or developing.

'muscle' comes from the Latin word 'musculus', meaning 'little mouse', and 'building' comes from the Old English 'byldan', meaning 'to construct'.

Initially, 'muscle-building' referred to the literal construction of muscle tissue, and this meaning has remained consistent in modern usage.