analysis - What does the title of The Discreet Charm of the Bourgeoisie mean, especially the Discreet Charm part? - Movies & TV

This 1972 movie, co-written and directed by the surrealist Luis Bunuel. I never actually get what is this the title about, especially "discreet charm".

Foremost, why is it "discreet"? Secondly, is the word "charm" used ironically, since some may find this movie freaky even without making any extra connection of what it is about.

Then, what does "discreet charm" mean together?
From here I think I could figure out the rest, but more explanation is always welcome. <;)