'nonseptic' originates from English, specifically formed from the negative prefix 'non-' (from Latin/Old English usage meaning 'not') and 'septic' which ultimately comes from Greek 'sēptikos' meaning 'causing putrefaction' (via Latin 'septicus').

'septic' changed from Greek 'sēptikos' to Latin 'septicus', entered medical/Latin usage and then Middle/Modern English as 'septic'; 'nonseptic' is a modern English formation created by adding the prefix 'non-' to 'septic'.

Initially, 'septic' meant 'causing putrefaction'; over time it broadened to mean 'infected or associated with sepsis' in medical contexts. 'nonseptic' has retained the straightforward negated sense 'not septic'.