Et tu, Brute?

The name Brutus, a second declension masculine noun, appears in the phrase in the vocative case, and so the -us ending of the nominative case is replaced by -e.[9] On March 15 (the Ides of March), 44 BC, the historic Caesar was attacked by a group of senators, including Brutus, who was Caesar's friend and protégé.

Suetonius mentions the quote merely as a rumor, as does Plutarch who also reports that Caesar said nothing, but merely pulled his toga over his head when he saw Brutus among the conspirators.

The phrase had also occurred in another play by Shakespeare, The True Tragedie of Richard Duke of Yorke, and the death of good King Henrie the Sixth, with the Whole Contention betweene the two Houses Lancaster and Yorke of 1595, which is the earliest printed version of Henry VI, Part 3.

[14] One theory states that the historic Caesar adapted the words of a Greek sentence which to the Romans had long since become proverbial: the complete phrase is said to have been "You too, my son, will have a taste of power", of which Caesar only needed to invoke the opening words to foreshadow Brutus's own violent death, in response to his assassination.

[15] The poem Satires; Book I, Satire 7 by Horace, written approximately 30 BC, mentions Brutus and his tyrannicide; in discussing that poem, author John Henderson considers that the expression E-t t-u Br-u-t-e, as he hyphenates it, can be interpreted as a complaint containing a "suggestion of mimetic compulsion".