The quote "A knavish speech sleeps in a fool's ear," from Shakespeare's play Hamlet, suggests that cunning or deceitful remarks are often not recognized or understood by those who lack wisdom. It implies that those who are gullible or foolish are easily swayed by manipulative words since they do not have the discernment to see through the deceit. In this way, the fool is more susceptible to being misled by clever or dishonest speech.

This line reflects a common theme in literature: the disparity between appearance and reality, as well as the nature of foolishness. It highlights how intelligence and discernment are crucial in discerning the truth behind words, particularly in a context where deception may be at play. Shakespeare's insight into human folly serves as a reminder of the importance of critical thinking in communication.