Green’s Dictionary of Slang

(drugs) marijuana.

1940		‘Jargon of Marihuana Addicts’ in AS XV:3 Oct. 336/2: The cigarettes are usually called reefers, but other names are: [...] greefas, greetas, grifas, grifos.
1949		Monteleone Criminal Sl. (rev. edn) 108: greta Marihuana.
1952		Lannoy & Masterson ‘Teen-age Hophead Jargon’ AS XXVII:1 26: GRETA, n. Marijuana.
1969		R.R. Lingeman Drugs from A to Z (1970) 105: greta [...] marijuana.
1980		‘Gloss. of Drug Terms’ National Instit. Drug Abuse.
2001		ONDCP Street Terms 11: Greeter — Marijuana [...] Greta — Marijuana.