'muscle-bound' originates from the English words 'muscle' and 'bound,' where 'muscle' refers to the tissue in the body that can contract to produce movement, and 'bound' means 'tied or fastened.'

'muscle-bound' evolved from the combination of 'muscle' and 'bound' in English, reflecting the idea of being constrained by one's own muscles.

Initially, it meant 'having muscles that restrict movement,' and this meaning has largely remained the same in modern usage.