Tabard is a short cape or coat bearing a coat of arms worn over a knight’s armor or by a herald.
Eucatastrophe is a word coined by Tolkien himself. It describes an unlooked for change in fortune or a surprise victory from the jaw’s of defeat. See: Helm’s Deep/ the Charge of the Rohirrim, the flight of the Eagles, the Pellenor Fields, etc.
Redoubt is a small, defensive fortification.