First Movie. Why does Norrington said to Jack ,,think about all the different meanings of silent as the Grave,,?

Around 1:41:00 after the Royal Navy saved Elisabeth and Jack from Rum Island he demanded the heading for the Isla de la muerte and to follow his Guards to the jail where he has a lot of time of thinking about all different meanings of the phrase silent as the Grave.

I guess i´m stupid. Why or about what should he be silent?

The cursed Gold?

Just stop talking nonsense?

Him being saved by the Navy?