'non-' + 'breeding' — the prefix 'non-' comes from Latin 'non' meaning 'not', attached to 'breeding', which is the noun/gerund form of the verb 'breed'.

'breed' originates from Old English 'brēdan' (to produce, give birth), which developed into Middle English 'breden'/'breed' and later formed compounds and modifiers such as 'non-breeding' by adding the negative prefix 'non-'.

Originally 'breed' meant 'to produce or bring forth young'; 'non-breeding' has retained the core sense of 'not breeding' and has also come to be used in ecological contexts to denote periods or individuals not engaged in reproduction.