'ataxonomic' originates from Greek elements: the privative prefix 'a-' (meaning 'not') combined with 'taxonomic', from Greek 'taxis' meaning 'arrangement' and 'nomos' meaning 'law' or 'custom'.

'ataxonomic' was formed in scientific/technical usage via New Latin or Modern Latin formations (e.g. 'ataxonomicus') from the Greek elements 'a-' + 'taxonomikos', and was later adopted into English as 'ataxonomic'.

Initially it conveyed the basic sense 'not arranged' or 'without taxonomic order'; over time it has retained that core meaning but has also been used more broadly to mean 'unsystematic' outside strict taxonomic contexts.