Green’s Dictionary of Slang

1. (US) a locust.

1878		J.H. Beadle Western Wilds 611: Went out one fine sunny morning about the first of June, and thought, by jiminy, the whole ground was moving. Ten million hoppers to the square yard.
1885		Omaha Dly Bee (NE) 10 June 7/4: On Wednesday last the hoppers began to attack the region [...] three to ten of the insects could be counted on each stick of grain.

2. (Irish) a flea (def. in cite 1852: ‘flies’ maybe misinterpretation).

1852		Kendal Mercury 17 Apr. 6/1: Blow me [...] if that ken of Beggar-me-Out’s vasn’t crammed full of chats (lice) and hoppers (flies).
1867		Sportsman 26 Sept. 2/1: Notes on News [...] An eminent German statistician [...] is making elaborate calculation [...] of the number of fleas that exist [...] to find out the strength of the ‘hoppers’ that infest [...] living things would indeed be cheerful acquisition to our knowledge.
1890		Sporting Times 18 Jan. 1: Most Hoppers in Three Minutes for Ten Scudi.
1903		G.D. Chase ‘Cape Cod Dialect’ in DN II:v 298: hopper, n. In expression ‘mad as a hopper‘.
c.1940–5		‘Myles na gCopaleen’ Best of Myles (1968) 152: This man is infested be hoppers.
1994		(con. 1920–30s) K.C. Kearns Dublin Tenement Life 61: Sure, the bed was loaded with bugs and hoppers and you’d be scratching yourself.

3. (US drugs) a drug runner.

2002

Simon & Burns ‘The Detail’ Wire ser. 1 ep. 2 [TV script] Motherfuckers beat my boy down. Little hoppers in the low-rises .