Literally: the habit doesn’t make the month Meaning: Don't judge a book by its cover. The suit doesn’t make the man.
Origins: From proverb that originated in the 13th century and would come from the medieval Latin language, from Plutarque's expression "barba non facit philosophum", translated as the beard doesn't make the philosopher.
Other sources cites an historical 1297 fact. In order to invade the Monaco fortress, Francois Grimaldi and his soldiers disguised as Franciscan monks to penetrate in the closed city. Another possible source ,came from the everyday life of monks, some didn’t sometimes quite follow the Church’s principles and their habit's rules..