Source : Webster's Revised Unabridged Dictionary (1913)

Merriness \Mer"ri*ness\, n.
   The quality or state of being merry; merriment; mirth;
   gayety, with laughter.

Source : WordNet®

merriness
     n : the trait of merry joking [syn: {jocoseness}, {jocosity}, {humorousness}]