Note to Romeo and Juliet, 2.2.161: "Else would I tear the cave where Echo lies, / And make her airy tongue more hoarse than mine"

Romeo and Juliet,
Act 2, Scene 2, line 161.
Echo: In Greek mythology, Echo was a nymph and Zeus loved consorting with beautiful young nymphs on Earth. Eventually, Zeus's wife, Hera, became suspicious, and descended from Mt. Olympus to catch Zeus with the nymphs. Echo, by trying to protect Zeus, became a target of Hera's wrath who put a spell on Echo so she is only able to speak the last few words spoken to her, like an echo. [So when Echo met Narcissus and fell in love with him, she was unable to tell him how she felt and was forced to watch him as he fell in love with himself.]

Echo by Alexandre Cabanel, 1874