Why is the ninth month called September?
c.1200, from Old French baniere (Modern French bannière) "flag, banner, standard," from Late Latin bandum "standard," borrowed from a West Germanic cognate of Gothic bandwa "a sign" (see band (n.2)). Figurative use from early 14c. Of newspaper headlines, from 1913.
(1.) The flag or banner of the larger kind, serving for three tribes marching together. These standards, of which there were four, were worked with embroidery and beautifully ornamented (Num. 1:52; 2:2, 3, 10, 18, 25; Cant. 2:4; 6:4, 10). (2.) The flag borne by each separate tribe, of a smaller form. Probably it bore on it the name of the tribe to which it belonged, or some distinguishing device (Num. 2:2,34). (3.) A lofty signal-flag, not carried about, but stationary. It was usually erected on a mountain or other lofty place. As soon as it was seen the war-trumpets were blown (Ps. 60:4; Isa. 5:26; 11:12; 13:2; 18:3; 30:17; Jer. 4:6 21; Ezek. 27:7). (4.) A "sign of fire" (Jer. 6:1) was sometimes used as a signal. The banners and ensigns of the Roman army had idolatrous images upon them, and hence they are called the "abomination of desolation" (q.v.). The principal Roman standard, however, was an eagle. (See Matt. 24:28; Luke 17:37, where the Jewish nation is compared to a dead body, which the eagles gather together to devour.) God's setting up or giving a banner (Ps. 20:5; 60:4; Cant. 2:4) imports his presence and protection and aid extended to his people.