The Collaborative International Dictionary of English v.0.48:

Skean \Skean\, n. [Ir sgian; akin to Gael. sgian, W. ysgien a
   large knife, a scimiter.]
   A knife or short dagger, esp. that in use among the
   Highlanders of Scotland. [Variously spelt.] "His skean, or
   pistol." --Spenser.
   [1913 Webster]