Green’s Dictionary of Slang

1. (drugs) to desire narcotics.

1921		Mencken Amer. Lang. (2nd edn) 108: A great many of them have remained Californian localisms, among them such verbs as to yen (to desire strongly, as a Chinaman desires opium) .
1933		Ersine Und. and Prison Sl.
1953		‘William Lee’ Junkie (1966) 63: You know yourself when a guy is yenning, he doesn’t look around behind him. He’s running.
1969		R.R. Lingeman Drugs from A to Z (1970) 251: yenning [...] Experiencing withdrawal symptons.

2. to desire someone or something.

1939		W. Winchell On Broadway 25 Apr. [synd. col.] He always yenned to be an actor.
1952		Lait & Mortimer USA Confidential 163: A busty blonde box-office draw got 20,000 oil dollars for a night with a Texan who had always yenned for her.
2010		IOL News (Western Cape) 2 Nov. 🌐 You just yening for apartheid times. Well, we got news for you, they are gone.