No one seems to know when man first cultivated millet, but there's general agreement that it originated in either Asia or Africa. The first official reference to millet is in the Fran Shen-Chiu Shu, the rural edict gathered in 2800 BC, making it one of the five sacred crops of China (the others being soybean, rice, wheat and barley). Millet swayed from the top of the hanging gardens of Babylon. (Herodotus wrote that the millet was so tall, he would not reveal its true height for fear of being taken as a liar.) At the foot of the Colossus in Rhodes, millet grew so thick, it obscured the base of the statue. In the Old Testament, millet was called "the gruel of endurance", not for its weather resistance but because of its nutritional benefits. In many ancient, diverse cultures - Roman, Greek, Gallic, Persian, Etruscan, Assyrian, Tartar and Visigoth - millet was consumed as a porridge, not only for its nutritional value but especially because of the common belief that millet protected the body and mind from "a mischievous world."
In North America, almost the entire crop is used as the main ingredient in birdseed, and only a tiny portion of the harvest is allocated for humans, but some cultures consume it as commonly as rice or barley, as in Mauritania, Egypt and Ethiopia.
From The Food Encyclopedia by Jacques Rolland and Carol Sherman
