'radiation-emitting' originates from Latin, specifically the words 'radiatio' (from 'radiare') and 'emittere', where 'radiare' meant 'to emit rays' and 'emittere' (from 'em-' + 'mittere') meant 'to send out'.

'radiation' entered English via Medieval Latin 'radiatio' and Old French forms before becoming 'radiation' in Middle English; 'emit' comes from Latin 'emittere' (through Old French/Middle English); the modern compound adjective 'radiation-emitting' is formed in modern English by combining these elements.

Initially the component words referred to 'sending out rays' and 'sending out'; over time the combined expression evolved to the current concise meaning of 'giving off radiation'.