One of Shakespeare’s most oft quotes lines, et tu, Brute? are the final words spoken by Julius Caesar in the play of that name. It means something like ‘You too, Brutus?’ or ‘Even you, Brutus?’. Even during the shock of assassination, there was room for further disbelief at Brutus’ involvement.
According to one ancient biographer, Plutarch, no such utterance was made. His account; ‘Some say that he fought and resisted all the rest, shifting his body to avoid the blows, and calling out for help, but that when he saw Brutus' sword drawn, he covered his face with his robe and submitted, letting himself fall.’ Another, Suetonius, has him exclaim ‘You too, young man?’ instead. But not in Latin. In Greek; καὶ σὺ, τέκνον;
But why Brute and not Brutus? The answer is this; some Latin Nouns have a special form used for addressing someone (or something) directly. The form is called the Vocative. Mostly, the vocative looks and sounds exactly like the Nominative. But for some nouns (Second Declension Masculine Nouns in the Singular to be exact) the Vocative looks and sounds a little different.
So, Brutus might be Brutus, but to greet Brutus you would say salve, Brute! To greet Marcus, salve, Marce! To greet Antonius and Gaius, salvete Antoni et Gai. To greet ‘my’ dear son (meus filius carus), salve, mi fili care! To greet Alan the barber and Claudia, salvete, Alane tonsor et Claudia. (Neither tonsor nor Claudia are Second Declension Masculine Nouns).
Today Alan is working in the barber shop. Claudia enters. ‘Salve, Alan,’ Claudia says. ‘Salve Claudia’, Alan responds.