Green’s Dictionary of Slang

horsefeathers n.

also feathers
[euph. for horseshit n.; supposedly coined by the comic strip artist William de Beck]

(orig. US) nonsense, rubbish; also as adj.

[US]Edwardsville Intelligencer (IL) 14 Sept. 4/4: The Flappers’ Dictionary [...] Feathers: Light conversation.
[US]T. Thursday ‘And Howe’ in Everybody’s Feb. [Internet] Once upon a time a snappy old hombre named George Bernard Shaw [...] proceeded to dash off the following load of horse feathers.
[US]W. Winchell On Broadway 11 Jan. [synd. col.] As for their theories, the Americans have a word for it – ‘bunk!’ . . . . B – as in Baloney, U – as in U-said-it, N- as in Nothin’ doing! and K – as in Horsefeathers!
[US]W. Winchell 5 Feb. [synd. col.] That’s what you call Horse-Sense – not Horse-Feathers.
[US]Mad mag. Aug.–Sept. 54: Horse-feathers – the same [i.e. expression of disbelief].
[US]‘Tom Pendleton’ Iron Orchard (1967) 319: Horse-feathers! Have an accident!
[US]G. Cuomo Among Thieves 383: All your horsefeathers ideas, turning this place into a mollycoddling bed of roses.
[US](con. 1916) G. Swarthout Tin Lizzie Troop (1978) 124: Let it make a jackass of itself as he had of himself [...] shouting ‘Horsefeathers!’.
[US]W. Kotzwinkle Midnight Examiner (1990) 191: I tried to always stay bouncy and bright. Well, horsefeathers on that! Do you hear me? Horsefeathers on it.