When Macduff's son defends his father's honor when the murderers sent by Macbeth call Macduff a traitor in Macbeth, they wind up stabbing the son:
FIRST MURDERER: Where is your husband?
LADY MACDUFF: I hope, in no place so unsanctified where such as thou mayst find him.
FIRST MURDERER: He’s a traitor.
SON: Thou liest, thou shag-ear’d villain!
FIRST MURDERER: What, you egg! [Stabbing him.] Young fry of treachery!
What's up with the "What, you egg!" line? Why does the murderer call the son an egg? It seems completely unrelated to anything else, and doesn't seem like a witty comeback to the son's "shag-ear'd villain" insult.