A piece of armor for the thighs, forming an appendage to the ancient corselet. Usually the tasse was a plate of iron swinging from the cuirass, but the skirts of sliding splints were also called by this name.
1786, Francis Grose, A Treatise on Ancient Armour and Weapons, page 21:This included the head-piece and gorgett, the back and breast, with skirts of iron called tasses or tassets covering the thighs, as may be seen in the figures, representing the exercise of the pike, published anno 1622, by the title of the Military Art of Training; the same kind of armour was worn by the harquebusiers.
