I remember bijou, from the list of French words that form plural by adding "x": bijou, caillou,chou, genou, hibou, jeujeu, pou. But I have never heard it mean anything but
"jewel".
"They were all displayed in that chamber of the Castle into which I had been first inducted, and which served, not only as the general sitting-room but as the kitchen too, if I might judge from a saucepan on the hob, and a brazen bijou over the fireplace designed for the suspension of a roasting-jack."

ijou
adj : small and elegant; "bijou villas"; "can Americans be
persuaded to pay out dollars for bijou cars?"
n : a small and delicately worked piece


Source: Webster's Revised Unabridged Dictionary (1913)

Bijou \Bi*jou"\, n.; pl. Bijoux. [F.; of uncertain origin.]
A trinket; a jewel; -- a word applied to anything small and
of elegant workmanship.

Also common as a movie theater name in the US back in the Good Old Days. We had a theater in Ithaca that, for its first few years of existence, ran movies from the '40s and '50s. It was called Fall Creek Pictures because of its location in the Fall Creek neighborhood, but I called it the Bijou. When they went from two screens to three I started calling it the Trijou.