The Tabard, in Southwark, is where Chaucer supposes his pilgrims to have assembled. The tabard was a jacket without sleeves, whole before, open on both sides, with a square collar, winged at the shoulder like a cape, and worn by military nobles over their armour. It was generally emblazoned with heraldic devices. Heralds still wear a tabard.
Item ... a chascun ung grand tabart De cordelier, jusques aux pieds.
Le Petit Testament de Maistre Franpois Villon.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894