<P> Still waters run deep is a proverb of Latin origin now commonly taken to mean that a placid exterior hides a passionate or subtle nature . Formerly it also carried the warning that silent people are dangerous, as in Caesar's summing up of Cassius in William Shakespeare's play Julius Caesar I. 2.195--6: </P> <Dl> <Dd> <Dl> <Dd> <Dl> <Dd> Yon Cassius hath a lean and hungry look . </Dd> <Dd> He thinks too much . Such men are dangerous . </Dd> </Dl> </Dd> </Dl> </Dd> </Dl>

What is the meaning of the proverb still waters run deep