Knowledge dropping

Honi soit qui mal y pense

I do wonder why this phrase was adopted for British passports, courts of law and sovereigns when, when people ask me what it means and why it is there, I have to give such an absurd explanation.



"Yes, I know what that means",  I can reply to the interrogator.  "It was said by one of our kings - they spoke French in those days - when he put on womenfolk's underwear in a public place, and it is a remonstrance of anyone who might snigger at him."
I am not unused to baffling my audience, but I do pity them at this point and their utter confundity as to why the Brits then emblazoned it upon everywhere official-looking that they could.
So if anyone has a worthier explanation (though I've a misplaced respect for the wits whose ridiculous reasons gain currency) please let me know.