The Collaborative International Dictionary of English v.0.48:
Humorousness \Hu"mor*ous*ness\, n. 1. Moodiness; capriciousness. [1913 Webster] 2. Facetiousness; jocularity. [1913 Webster]WordNet (r) 3.0 (2006):
humorousness n 1: the trait of merry joking [syn: jocoseness, jocosity, merriness, humorousness]