«قَالُوا: شَكَرْنَا غَنَّامْ. غَنَّامْ طِلِعْ حَرَامِي»

The saying describes a person whom others regarded as good, who then shows himself to be the very opposite of what was expected. Ghannam is a stock name standing for anyone, not a real individual, whose true character comes to light and clashes with the favorable opinion people had of him.

Its force lies in the sharp turn between two short statements: first the speakers' kind words about Ghannam, then the plain discovery that he is a thief. The point is that his nature is revealed, not that he changed, and placing the statements side by side makes the gap between expectation and reality unmistakable.

Said of someone who had been thought well of and then emerges as quite different from the goodness people assumed in him. It fits moments when a person's conduct reveals a character at odds with the favorable view others had held.