The fable is that this cow belonged to a giant, and was kept on Mitchell Fold (middle fold), Shropshire. Its milk was inexhaustible; but one day an old woman who had filled her pail, wanted to fill her sieve as well. This so enraged the cow, that she broke loose from the fold and wandered to Dunsmore Heath, where she was slain by Guy of Warwick.
Isaac Taylor, in his Words and Places (p. 269), says the dun cow is a corruption of the Dena Gau or Danish settlement in the neighbourhood of Warwick. Gau, in German, means region, country. If this explanation is correct, the great achievement of Guy of Warwick was a victory over the Danes, and taking from them their settlement near Warwick.
DunCow of Warwick: A monstrous cow which was supposed to have come from Shropshire in the tenth century, where she provided milk for local giants.
The DunCow roared and thundered towards him, he threw his bow to the ground and drew his axe and stood his ground as the beast slammed into him piercing his armour as he struck the animal a massive blow between the eyes.
The great DunCow was butchered and eaten by the local population and Guy was knighted and the king ordered that one of the cows ribs should be hung in Warwick Castle.