Green’s Dictionary of Slang

(US drugs) a marijuana cigarette.

1940		‘Jargon of Marihuana Addicts’ in AS XV:3 Oct. 336/2: The cigarettes are usually called reefers, but other names are: [...] miggles.
1949		Monteleone Criminal Sl. (rev. edn) 155: miggles Marihuana cigarettes.
1959		J.E. Schmidt Narcotics Lingo and Lore 110: Miggies [...] Miggles – Marihuana cigarettes.
1971		‘Hassan-i-Sabbah’ Leaves of Grass 1: Mary Warner / Miggles / Hemp.