Green’s Dictionary of Slang

1. (US) to fellate.

1929

implied in yodeler n.

2. (also grin in the canyon (of love), yodel, yodel from the highest tower, yodel down/in/up the valley) to perform cunnilingus;thus canyon yodeler, a cunnilinctor.

c.1935		‘Mae West in “The Hip Flipper”’ [comic strip] in B. Adelman Tijuana Bibles (1997) 95: Grasping our beauteous heroine by the haunches he yodeled in the canyon to Lotta’s delight.
c.1935		‘Pete in “No Pay”’ [comic strip] in B. Adelman Tijuana Bibles (1997) 43: I’d never yodled [sic] in the valley before.
c.1938		‘You Nazi Man’ [comic strip] in B. Adelman Tijuana Bibles (1997) 131: The great Hipler grins in the grip, snorts in the gulley, yodels in the canyon and sneezes in the satchel.
1939		‘Hotel Sl.’ in AS XIV:3 Oct. 240/2: to yodel To indulge in unnatural intercourse.
1941		G. Legman ‘Lang. of Homosexuality’ Appendix VII in Henry Sex Variants.
1963–74		B. Humphries Barry McKenzie [comic strip] in Complete Barry McKenzie (1988) 74: If you wanted to yodel up the valley youse had your chance back in the studio.
1964		R. Abrahams Deep Down In The Jungle 214: [O]ld dirty slim was what you would call a bushwacker, a nose diver, a canyon yodler, well in other words a cocksucker, or just say that he ate pussy. He was also a puck lover, and a whore mongler, in other words he was just plain dirty Slim to everyone.
1965		Guild Dict. Homosexual Terms 50: yodel in the canyon (of love) (v.): To practice cunnilinctus; very widely used in the U.S.A.
1972		B. Rodgers Queens’ Vernacular.
1980		E. Folb Runnin’ Down Some Lines 155: Eatin’ pussy. I don’t do none dat canyon stuff! [Ibid.] 158: Expressions [...] that are [...] euphemistic (to dive/yodel/sneeze/grin in the canyon). [Ibid.] 231: canyon, dive/grin/sneeze/yodel in the Engage in cunnilingus.
1999		D. Lypchuk ‘A dirty little story’ in eye mag. 8 July 🌐 On the jewelled terrace he growled at the badger, blew some tunes and went way down south in Dixie, where he found himself grinning in the canyon.
2000		‘Be A Cunning Linguist’ in Maxim Feb. 🌐 Yodel down the valley: Gunter was too tired to talk, having spent most of the day yodeling down the valley.
2003		Indep. Rev. 1 Oct. 5: He does indeed yodel from the highest tower.