Wing of a house, wing of an army, wing of a battalion or squadron, etc., are the side-pieces which start from the main body, as the wings of birds.
“This sound of danger lent me wings.”
R. L. Stevenson.
To take one under your wing. To patronise and protect. The allusion is to a hen gathering her chicks under her wing.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894