word-forming element meaning "air, atmosphere; gases," in 20c. use with reference to aircraft or aviation, from Greek aēr (genitive aeros) "air, lower atmosphere" (see air (n.1)).
1740, "unwholesome air, air contaminated with the poison producing intermittent and remittent fever," from Italian mal'aria, from mala aria, literally "bad air," from mala "bad" (fem. of malo, from Latin malus; see mal-) + aria "air" (see air (n.1)). Probably first used by Italian physician Francisco Torti (1658-1741). By 1866 it had come to be used of the disease itself (earlier malaria fever, by 1814). The disease, now known to be mosquito-borne, once was thought to be caused by foul air in marshy districts. Replaced native ague.