當麥克白送來的殺人犯稱麥克達夫為麥克白的叛徒時，麥克達夫的兒子為父親的榮譽辯護時，他們刺死了兒子：
Enter Murderers.
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!
-Macbeth
"怎麼了，你雞蛋！"線？兇手為什麼叫兒子一個雞蛋？這似乎與其他任何事物都毫無關係，而且似乎也不是兒子的" sha腳的小人"侮辱的機智的捲土重來。
A. R. Braunmuller (Macbeth, New Cambridge Shakespeare, 1997) provides the following gloss:
Contemptuous epithet for a young person (OED Egg sb 2b, citing only this line and another from 1835); (...)
G. K. Hunter's edition of the play (New Penguin Shakespeare, 1967) doesn't provide a gloss here.
Braunmuller also links the murderer's word choice with the proverb "An evil bird lays an evil egg" (cited in Robert W. Dent's Shakespeare's Proverbial Language: An Index, 1981, B376).
The murderer also calls Macduff's son "fry of treachery". Fry means fish-spawn (G. K. Hunter) or "progeny, (...), brood" (Wiktionary) and is another "contemptuous epithet". It is also worth noting that the word choice "egg" fits the bird imagery in Macbeth.
When Shakespeare uses an unfamiliar or idiomatic word or phrase, he quite often doubles it with a more conventional one, with the effect of explaining it "in place." There's a good example of this elsewhere in Macbeth, when the eponymous villain says "Will all great Neptune’s ocean wash this blood clean from my hand? No, this my hand will rather the multitudinous seas incarnadine, making the green one red." Incarnadine is thus explained as making the green one red.
If we view the same technique at work here, then "egg" = "young fry of treachery." So Macduff Jr. is being here accused of following in the traitorous footsteps of his father. The apple does not fall far from the tree, nor the egg from the hen that laid it, being the general implication.
