What is the meaning of [Evil be to him who evil thinks]

The French for this, Honi soit qui al y pense, is the motto of the Most Noble
Order of the Garter, instituted by King Edward III in about 1344. A more
correct translation is ‘Dishonour be to him who thinks evil of it’ – i.e. the
order. Sir Walter Scott says in his _Essay on Chivalry_ that the motto seems
to apply to possible misrepresentations that King Philip of France might seek
to make concerning the order.