From a town in Denmark, which is said to take its name from a river with which it is watered that drives several mills. Roe, in the ancient Danish language, signifies a king, and kille, a stream of water or brook, i. e., the king’s brook. Some have given the signification “Red—shield” to the name, from Roth, red.

Arthur, William (1857) An Etymological Dictionary of Family and Christian Names. New York: Sheldon, Blakeman. Public Domain.

ROTHSCHILD. Whatever may have been the origin of this name, its component parts are the German for " red shiekl," and it is not improbable that it was originally assumed, in chivalric times, by one who chose to carry a weapon of that colour. There are several instances of some peculiarity in the weapons of ancient warriors having given rise to sobriquets, and even to transmissible or family names, such as Lougespee, Strongbow, Fortescue, Brownsword. We have also an authenticated instance of an ' armiger ' who chose to bear his ensigns with the single tincture Gules, or red. In the curious heraldric poem on the Siege of Carlaverock, A.D. 1300, one of the commanders is described as bearing, not indeed a shield, but a banner, entirety red : —

Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.