Golapas
A giant, who fought with the Romans against Arthur, killed at the battle of Soissons (the final battle of the Roman War).
[Galapas] was a man of an huge quantity and height, [Arthur] shorted him and smote off both his legs by the knees, saying, Now art thou better of a size to deal with than thou were, and after smote off his head.
His literary roots may cross paths with the giant Galaas and the fountain of Galabes.
Sources
Alliterative Morte Arthure | c. 1400
Le Morte Darthur | Sir Thomas Malory, 1469-1470