whimsey

But if it calms you to play like this, I am ready to humour so ridiculous a whimsey.'

I'm all right, I'm gettin' on all right,'an' then 'e went; seemed to go ower the whimsey an' back towards th' wood.

Geoffrey Montfichet's reason for wishing to be known as the Scarlet Knight was no idle whimsey, as the others had guessed.

The whole affair was the mere whimsey of his own freakish imagination.