The Collaborative International Dictionary of English v.0.48:

Sicilian \Si*cil"i*an\, a.
   Of or pertaining to Sicily or its inhabitants.
   [1913 Webster]

   Sicilian vespers, the great massacre of the French in
      Sicily, in the year 1282, on the evening of Easter Monday,
      at the hour of vespers.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Vespers \Ves"pers\, n. pl. [OF. vespres, F. v[^e]pres, LL.
   vesperae, fr. L. vespera evening. See Vesper, n.] (R. C.
   Ch.)
   (a) One of the little hours of the Breviary.
   (b) The evening song or service.
       [1913 Webster]

   Sicilian vespers. See under Sicilian, a.
      [1913 Webster]