the red banner of St. Denis, near Paris, carried before the early kings of France as a military ensign.
2.
any ensign, banner, or standard, especially one that serves as a rallying point or symbol.
Origin: 1425–75; late Middle English oriflam < Middle French oriflamme,Old French, equivalent to orie golden (< Latin aurea, feminine of aureus, derivative of aurum gold) + flammeflame