In 360 BC near ancient Athens there was a gymnasium (gym) in which those who did not have both parents come from Athens. Its name was Kynosarges (in ancient Greek this meant white dog) and according to the legend it comes from a big white dog. Legend has it that the Athenians were preparing to offer a sacrifice to Hercules when a white dog (Kynos - Argos) snatched the thighs of the sacrificial animal and, being persecuted by the people, abandoned them a bit further away. The Athenians, in order to atone for Hercules, received an godly order to build a small temple at this point and because of the dog they named it Kynosarges. The word Argos in ancient Greece translates to fast or white.
Another reference to a possibly white dog was that of Odysseus, who waited 20 years for his alpha to return home before taking his last breath. He was also called Argos.
Of course we are not talking about the Greek White Shepherd, but about large white dogs that lived in Greece many years ago and were the predecessors of today's Greek dogs. These were not specialized dogs such as shepherds or hounds, as the kennels had not yet been developed enough to specialize in dogs.