The Collaborative International Dictionary of English v.0.48:

Holyday \Ho"ly*day`\, n.
   1. A religious festival.
      [1913 Webster]

   2. A secular festival; a holiday.
      [1913 Webster]

   Note: Holiday is the preferable and prevailing spelling in
         the second sense. The spelling holy day or holyday in
         often used in the first sense.
         [1913 Webster]