[W march, horse].
Early Welsh legendary hero and an antecedent of the Arthurian King Mark. The Welsh Triads refer to him as one of the Three Seafarers of the Isle of Britain, and historical records show him as the son of a king of Glamorgan who granted lands to St Illtud. Allusions to March exist in Breuddwyd Rhonabwy [The Dream of Rhonabwy] and the gnomic poetry known as Englynion y Bidiau. More recent folklore places March at Castell March in Lly^n, Caernarvonshire, in north-western Wales. Here he shares the affliction of the Irish king Labraid Loingsech of having horse's ears, making word-play with his name; in shame he grows his hair long to cover them and has his barbers murdered. In Welsh Arthurian stories March is the king of Cornwall in the love triangle with Tristan and Iseult. The King Mark of international Arthuriana draws also from other antecedents.
See John James Jones, ‘March ap Meirchion: A Study in Celtic Folk-Lore’, Aberystwyth Studies, 12 (1932), 21–33.