Following the fall of the Roman empire, the tunic continued to be worn with varying sleeve and hem lengths throughout Europe during the Middle Ages. Often reaching the knees or ankles, it was usually worn over underclothes consisting of a shirt (usually hip-length or longer) and drawers (usually knee- or ankle-length pants related to braccae). It may be accompanied by hose.
Tunics worn during the Early Middle Ages often featured decorative embroidery or tablet-woven braids along the neck, hem and wrists. This was the case, for instance, with tunics worn by both rich and poor Anglo-Saxons before the Norman Conquest.("Tunic." Wikipedia, The Free Encyclopedia.)
A Tabard (from the French tabarde) was originally a humble outer garment of tunic form, generally without sleeves, worn by peasants, monks and foot-soldiers, including Chaucer's ploughman. In this sense the first OED citation is 1300. In the late middle ages tabards, now open at the sides and so usually belted, were worn by knights over their armour, and usually emblazoned with their arms (though sometimes worn plain).("Tabard." Wikipedia, The Free Encyclopedia.)