Green’s Dictionary of Slang

(drugs) marijuana.

1938		R.P. Walton Marihuana 24: Lucien and Doria say that the ‘maconha’ smoked in Brazil is an African variety of cannabis. Iglesias reported in 1918 that the practice was extremely prevalent in Brazil.
1969		R.R. Lingeman Drugs from A to Z (1970) 153: macon [West Africa] cannabis. maconha [Brazil] cannabis.
2001		ONDCP Street Terms 14: Macon [...] Maconha — Marijuana.