Meaning

verb expose to fresh air

noun the opening of a subject to widespread discussion and debate

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