'radiation-absorbing' is a modern English compound formed from the noun 'radiation' and the present participle 'absorbing' (from the verb 'absorb'). 'radiation' originates from Latin, specifically the word 'radiatio', where 'radius' meant 'ray' or 'beam'. 'absorb' originates from Latin, specifically the word 'absorbere', where the prefix 'ab-' meant 'away' and 'sorbere' meant 'to suck in'.

'radiation' changed from Latin 'radiatio' through Old French/Middle English forms (e.g. Middle English 'radiacioun') into modern English 'radiation'. 'absorb' transformed from Latin 'absorbere' to Old French/Middle English forms (e.g. 'absorben') and became modern 'absorb'. The compound 'radiation-absorbing' arose in modern English by combining these elements to describe materials or substances that absorb radiation.

Initially, 'radiation' meant 'a shining forth' or emission of rays; over time it came to mean energy emitted as rays or particles (including electromagnetic and ionizing radiation). 'absorb' originally meant 'to suck in' and has largely retained the sense of taking in; together the compound came to mean 'capable of taking in or absorbing radiation'.