Brewer's: Fiddle-faddle

It is all fiddle-faddle. Rubbishy nonsense; talk not worth attention. A ricochet word, of which we have a vast number, as “flim-flam,” “helter-skelter,” “wishy-washy,” etc. To fiddle is to waste time in playing on the fiddle, and hence fiddle means a trifle, and fiddle-faddle is silly trifle or silly nonsense.

“Pitiful fool that I was to stand fiddle-faddling in that way.” Clough: Amours de Voyage, canto iv. stanza 3.

Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894

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Fiddle-de-dee!