The Collaborative International Dictionary of English v.0.48:

Sabretasche \Sa"bre*tasche`\, n. [F. sabretache, G.
   s[aum]beltasche; s[aum]bel saber + tasche a pocket.] (Mil.)
   A leather case or pocket worn by cavalry at the left side,
   suspended from the sword belt. --Campbell (Dict. Mil. Sci.).
   [1913 Webster]