Meaning

noun the opening of a subject to widespread discussion and debate

noun a short excursion (a walk or ride) in the open air

noun the act of supplying fresh air and getting rid of foul air

originFrom air (“substance constituting Earth’s atmosphere”, noun) and air (“to bring (something) into contact with the air; to let fresh air into (a place); to make public (an opinion, etc.); to broadcast (something)”, verb) + -ing (suffix forming nouns or noun-like terms from verbs, denoting acts of doing something, actions, or the embodiment of action; and forming the present participles of verbs).

Etymology from Wiktionary, CC BY-SA 3.0