E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A crotchet or peculiar one-sided view of a subject, a monomania. Properly a peculiar effect produced by medicines or foods; as when coffee acts as an aperient; the electrical current as an emetic, as it does upon me. (Greek, idios sun krasis, something peculiar to a persons temperament.)