The Plymales of the US claim that their ancestor(s) migrated from Brittany, in France. However I think the name may be French rather than Breton. There is a French surname, Plumail,which might be the original. The letter U in French is thin and might become an I or a Y when pronounced by English speakers. The surname derives from the word plume, and Jean Tosti speculates that it might be a nickname for someone who wore a feather in his hat. Plumail is found most frequently in the Mayenne region of France, which is next door to Brittany.