Sources : Megaris

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Fish 7.54): The megaris is a fish of the sea. It has a length of two palms. It is considered cheap in the parts where it is caught, but when taken to the more distant places the rarity of its saltiness makes it worth its price. However, serving it freshly caught and without salt makes the food more delicious for those who eat it. This fish signifies those, which, even if they are of lowly birth, because no prophet is accepted in his own country, are assigned by lot to honors and official positions when they come from unknown places. They can also signify those who, though their reputation and merits are low, are nevertheless exalted by the lowly and their ilk, either because they wished to have an equal in crime, or because they could not find any others worthy of honor. Hence the proverb of the Gauls: Because of the lack of a good man, a fool is placed in a high position. - [Badke translation/paraphrase]