late 14c., "action of making aromatic smoke as part of a ceremony," from Latin fumigationem (nominative fumigatio) "a smoking," noun of action from past participle stem of fumigare "to smoke," from fumus "smoke, fume" (see fume, n.) + root of agere "to drive" (see act, n.). Sense of "exposure (of someone or something) to aromatic fumes" is c.1400, originally as a medicinal or therapeutic treatment.