What is the source of Et tu, Brute? And, what was Shakespeare's source(s)

Factual Questions
1

See subject(s).

Thanks,

Leo

2

The main source for Shakespeare’s play Julius Caesar is Plutarch’s Lives of the Noble Greeks and Romans, particularly the chapters on Julius Caesar and on Brutus. However, Plutarch does not include the quotation “Et tu Brute?”

3

The “Et tu, Brute” line seems to be inspired by Suetonius, who says some writers report that Caesar said “You too, my child” in Greek when Brutus stabbed him. (Interestingly, it’s not in Plutarch’s Life of Brutus or Life of Caesar, which would have been Shakespeare’s most important sources for the majority of the play; in Plutarch, Caesar’s last words are “Accursed Casca, what does thou?”)