Source : Webster's Revised Unabridged Dictionary (1913)

Fog \Fog\ (f[o^]g), n. [Cf. Scot. fog, fouge, moss, foggage rank
   grass, LL. fogagium, W. ffwg dry grass.] (Agric.)
   (a) A second growth of grass; aftergrass.
   (b) Dead or decaying grass remaining on land through the
       winter; -- called also {foggage}. [Prov.Eng.]
       --Halliwell.

   Note: Sometimes called, in New England, {old tore}. In
         Scotland, fog is a general name for moss.