throw one's cap over the windmill

Probably a calque of French jeter son bonnet par-dessus les moulins ^[1]. Widely reported as deriving from a passage in the novel Don Quixote in which the titular character throws his cap over a windmill that he has mistaken for a giant, as a challenge. However, no such passage exists in the book.

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throw one's cap over the windmill (third-person singular simple present throws one's cap over the windmill, present participle throwing one's cap over the windmill, simple past threw one's cap over the windmill, past participle thrown one's cap over the windmill)

1. (idiomatic, dated) To act in a bizarre, eccentric or immoral manner.
   • 1892, Oscar Wilde, Lady Windermere's Fan, Act III:

     Awfully commercial, women nowadays. Our grandmothers threw their caps over the mills, of course, but, by Jove, their granddaughters only throw their caps over mills that can raise the wind for them.

   • 1914, E. A. Brayley Hodgetts, The Life of Catherine the Great of Russia‎^[1]:

     Even Catherine’s own mother scandalized her daughter by succumbing to the contagion of the place, and “throwing her cap over the windmill,” as the French have it.

   • 1934, Dorothy L. Sayers, The Nine Tailors:

     Besides, Suzanne had already thrown her bonnet over the windmill.