It's all Greek to me

This expression has Shakespearean origins. In the tragic play, Julius Caesar this expression occurs during a conversation between Casca and Cassius, two conspirators againt Julius Caesar. The pun comes from the fact that a Roman senator, Cicero is speaking Greek and his fellows don't understand him. The context is as follows:

Cassius: Did Cicero say anything?

Casca: Ay, he spoke Greek.

Cassius: To what effect?

Casca: Nay, an I tell you that, I'll ne'er look you i' the face again: but those that understood him smiled at one another, and shook their heads; but, for mine own part, it was Greek to me. I could tell you more news too: Marullus and Flavias, for pulling scarfs off Caesar's images, are put to silence. Fare you well. There was more foolery, if I could remember it.

"Panta" is neuter plural, and it agrees with "estin" because, for some totally mysterious reason, Greek neuter plural subjects always take singular verbs. "Emoi" is of course the dative of ego. I put "glotta" ("glossa" in Aeolic and other dialects) in to distinguish the Greek language from Greek things in general. In Latin this would be:

OMNIA MIHI LINGVA GRAECA SVNT.