The distinction between these two, in Swift's day, may be taken from the locus classicus on the subject (Spectator, No. 35). The genealogy of True Humour Addison gives thus:
'Truth was the founder of the family, and the father of Good Sense. Good Sense was the father of Wit, who married a lady of a collateral line, called Mirth, by whom he had issue Humour.'
So he gives Falsehood as the mother of Nonsense, who had a son called Frenzy, who married one of the daughters of Folly, commonly known by the name of Laughter, and 'begot that monstrous infant,' False Humour. The genealogy makes it clear that, in the well-defined sense of that day, Wit was purely intellectual; while to produce Humour, mirth had to be added. Now-a-days, each man seems to adopt his own interpretation. Cf. also the lines in Sheffields Essay on Poetry —
'That silly thing men call sheer wit avoid,
With which our age so nauseously is cloyed;
Humour is all: wit should be only brought
To turn agreeably some proper thought.'