'nonreduction' is formed from the prefix 'non-' (from Latin 'non', meaning 'not') plus 'reduction' (from Latin 'reductio', 'a leading back' or 'bringing back').

'reduction' originates from Latin 'reductio' > Old French/Medieval Latin forms > Middle English 'reduction'; the modern compound 'nonreduction' is a relatively recent, transparent formation using the negative prefix 'non-' + the noun 'reduction'.

Originally the elements meant 'not' + 'a bringing back' (in the root sense); in modern use the compound simply denotes 'the absence of reduction' and retains that literal negative meaning.