irradiation (n.)youdaoicibaDictYouDict[irradiation 词源字典]
1580s, from French irradiation, from Latin *irradiationem, noun of action from past participle stem of irradiare (see irradiate). Originally of light (literally and figuratively); of X-rays, etc., from 1901.[irradiation etymology, irradiation origin, 英语词源]