Is it a word really much in use or did you see it for the first time too?

It's common enough, but I haven't heard it used in a while. (The word seems just the teeniest bit old-fashioned and precious.) There's a Magdalen College at Oxford and a Magdalene College at Cambridge, and they are both pronounced /ˈmɔːdlɪn/.

Ceci n'est pas un seing.