The Collaborative International Dictionary of English v.0.48:

Lambrequin \Lam"bre*quin\, n. [F. Cf. Lamboys, Label.]
   1. A kind of pendent scarf or covering attached to the
      helmet, to protect it from wet or heat.
      [1913 Webster]

   2. A leather flap hanging from a cuirass. --Wilhelm.
      [1913 Webster]

   3. A piece of ornament drapery or short decorative hanging,
      pendent from a shelf or from the casing above a window,
      hiding the curtain fixtures, or the like.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mantling \Man"tling\, n. (Her.)
   The representation of a mantle, or the drapery behind and
   around a coat of arms: -- called also lambrequin.
   [1913 Webster]

WordNet (r) 3.0 (2006):

lambrequin
    n 1: a scarf that covers a knight's helmet
    2: short and decorative hanging for a shelf edge or top of a
       window casing