"You too, Brutus" or "even you, Brutus"; expression of betrayal.
Esimerkit
Prince Edward: Et tu Brute, wilt thou stab Cæsar too? A parlie sirra to George of Clarence.
[Casca stabs Cæsar in the Neck. Cæsar catches hold of his Arm. He is then stabbed by several other Conspirators, and at last by Marcus Brutus.] Cæsar: Et tu, Brute?—Then fall, Cæsar. [Dies. The senators and people retire in confusion.]
And that is the reason why a young buck with an intelligent looking calf's head before him, is somehow one of the saddest sights you can see. The head looks a sort of reproachfully at him, with an “Et tu Brute!” expression.
But according to the Oxford editor of Julius Caesar, 'Et tu, Brute' had probably already become a popular tag by the time of True Tragedy [see 1591 cite], readily understood by English speakers just as it is today.
"Et tu, Brute?" (3.1.76). This familiar but strange, strangely familiar, anachronistic foreign language at the heart of Julius Caesar is the only Latin in all of Shakespeare's so-called Roman plays.