As Jonathan Strange describes it in the prologue to his History, the person who in 1111 conquered Northern England at the head of a Sidhe army at first declared that he had no name. Later he was content to call himself after his putative father, John d'Uskglass. This may or may not have been his identity. Strange adds however that "in the early part of his reign he was known simply by one of the many titles his friends or enemies gave him: the King; the Raven King; the Black King; the King in the North" .
The by-name of "the Black King" of course may derive simply from a feature of his usual appearance. Although pale-skinned he has black hair and, moreover, a fondness for dressing in that colour. Strange tells us that even on first coming into the court of King Henry he wore "ragged clothes of coarse black wool". Later he seems to have worn finer (and cleaner) garments, but his preference for black evidently continued: certainly in the mural which Strange admires at Windsor he is depicted wearing "a black robe", and when seen by John Childermass he is again in "black boots and a black travelling coat".