Is this a real word?

Not sure if it's real, but it makes sense. It has an eponymous etymology: there was a king of Lydia, Candaules who told one of his guards to try to see his (i.e., Candaules') wife naked to prove her great beauty of which the king was always bragging. Herodotus told the story in his Histories 1.7.1.

[Candaules said] "Gyges, I do not think that you believe what I say about the beauty of my wife; men trust their ears less than their eyes: so you must see her naked." Gyges protested loudly at this. "Master," he said, "what an unsound suggestion, that I should see my mistress naked! When a woman's clothes come off, she dispenses with her modesty, too. Men have long ago made wise rules from which one ought to learn; one of these is that one should mind one's own business. As for me, I believe that your queen is the most beautiful of all women, and I ask you not to ask of me what is lawless."

Kind of reminds me of the long-suffering Griselda.

Ceci n'est pas un seing.