E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Honi soit qui mal y pense (Evil be [to him] who thinks evil of this). The tradition is that Edward III. gave a grand court ball, and one of the ladies present was the beautiful Countess of Salisbury, whose garter of blue ribbon accidentally fell off. The king saw a significant smile among the guests, and gallantly came to the rescue. Honi soit qui mal y pense (Shame to him who thinks shame of this accident), cried the monarch. Then, binding the ribbon round his own knee, he added, I will bring it about that the proudest noble in the realm shall think it an honour to wear this band. The incident determined him to abandon his plan of forming an order of the Round Table, and he formed instead the order of the Garter. (Tighe and Davis: Annals of Windsor.)