From the Old Welsh masculine name Morcant, which was possibly derived from Welsh mor "sea" and cant "circle". Since the 1980s in America Morgan has been more common for girls than boys, perhaps due to stories of Morgan le Fay.

Modern form of Morgen, which was used by Geoffrey of Monmouth in the 12th-century for the Arthurian sorceress Morgan le Fay, who was unnamed in earlier stories. Geoffrey probably did not derive it from the Welsh masculine name Morgan, which would have been spelled Morcant in his time. He may have based it on the Irish name MUIRGEN.