'nonparasitic' is formed by the prefix 'non-' (meaning 'not') attached to 'parasitic'. 'Parasitic' comes from 'parasite', ultimately from Greek 'παράσιτος' ('parasitos'), where 'para-' meant 'beside' and 'sitos' meant 'food'.

'παράσιτος' (Greek) became Latin 'parasitus' and Old French 'parasite', then Middle English 'parasite'; from this developed the adjective 'parasitic' (with suffix '-ic'), and later the negative prefix 'non-' was added to create 'nonparasitic'.

Originally 'παράσιτος' described a person who ate at another's table ('one who eats beside [another]'); over time it came to denote organisms that live on or in a host and derive nutrients at the host's expense; 'nonparasitic' now means 'not of that nature'—i.e., not living off a host.