irradiate
v. US //ˌɪˈɹeɪdiˌeɪt// UK //ɪɹˈeɪdɪˌeɪt// ir·ra·di·ate
From Middle English irradiate (“illuminated, shining”), borrowed from Medieval Latin irradiātus, perfect passive participle of irradiō, from ir- (“against; into; on, upon”) + radiō (“to cause to radiate, irradiate; to emit beams, radiate”), from radius (“ray of light; rod, staff; spoke of a wheel”) + -ō (first conjugation verb-forming suffix) (further etymology uncertain; possibly ultimately from Proto-Indo-European *reh₁t- (“beam; pole; post”)). The adjective is attested earlier than the verb. The English word is analysable as in- (“against; into; on, upon”) + radiate.
From Middle English irradiate (“illuminated, shining”) (more at etymology 1), see -ate (verb-forming suffix).