A similar garment with short sleemes or without sleeves was worn in the middle ages by knights over their armour, and was also emblazoned with their arms or worn plain.
The name was also given in earlier days to a much humbler similar garment of rough frieze worn by peasants; the ploughman wears a tabard in the Prologue to the Canterbury Tales. See all the Tabard Inn
Similarly at Queens College, Oxford, the scholars on the foundation were called tabarders, from the tabard, obviously not an emblazoned garment, which they wore.
It can also be the British English word for a cobbler apron.