Facetious, a. — Webster enters it under “facetious”
Etymology: [Cf. F. facétieux. See Facetiæ.]
1. Given to wit and good humor; merry; sportive; jocular; as, a facetious companion.
2. Characterized by wit and pleasantry; exciting laughter; as, a facetious story or reply. -- Fa*ce"tious*ly, adv. -- Fa*ce"tious*ness, n.
Shades of meaning
Fernald has no entry of its own for facetiousness; he lists it under wit.
He lists it without comment; the entries above explain its neighbors.