'nonclassical' originates from English, formed by the negative prefix 'non-' (from Latin 'non' meaning 'not') attached to 'classical' (from Latin 'classicus', meaning 'belonging to a class; first-class').

'classical' comes from Latin 'classicus' → Late Latin/Old French forms (e.g. 'classique') → Middle English 'classical'. The negative prefix 'non-' was used in English to form negations and was combined with 'classical' to produce 'nonclassical'.

Initially it simply meant 'not classical' (i.e., not belonging to or following classical style). Over time it has been extended in technical fields (notably physics) to denote phenomena that are fundamentally incompatible with classical explanations.