The Collaborative International Dictionary of English v.0.48:

Galligaskins \Gal`li*gas"kins\, n. pl. [Prob. corrupted fr. It.
   Grechesco Grecian, a name which seems to have been given in
   Venice, and to have been afterwards confused with Gascony, as
   if they came from Gascony.]
   Loose hose or breeches; leather leg quards. The word is used
   loosely and often in a jocose sense.
   [1913 Webster]