Green’s Dictionary of Slang

1. depressing.

1889		J.K. Jerome Three Men in a Boat 10: Harris said he thought it would be humpy. He said he knew the sort of place I meant; where everybody went to bed at eight o’clock.
1992		P. McCabe Butcher Boy 191: Go on you humpy bastard! I shouted after him.

2. (also humpsome) depressed, miserable.

1914		E. Pugh Cockney At Home 53: I do feel pretty humpsome at times.
1915		H. Chapin letter 12 Jan. in Soldier and Dramatist (1916) 62: To be among a lot of people who are half of them nursing grievances is rather depressing when one has quite enough to be humpy about without listening to others’ imaginary grievances.