'unmetabolized' originates from Old English prefix 'un-' (a negative prefix) combined with 'metabolize' which ultimately derives from Greek 'metaballein', where 'meta-' meant 'change' and 'ballein' meant 'to throw'.

'unmetabolized' developed as English adopted 'metabolize' from Late/Modern Latin and Greek ('metabole' / 'metaballein'), and the native Germanic prefix 'un-' was attached to form the adjective meaning 'not metabolized'.

Originally the Greek root related to 'change' (general change or transformation); over time in scientific usage it came to mean specific chemical change in living organisms (metabolism), so 'unmetabolized' now means 'not chemically changed by metabolism'.