The expression dates back to at least the early part of the 17th century. Two different playwrights of that period used it. Thomas Dekkar included it in his play: “Patient Grissel,” in 1603 as follows: “FAR: Asking for some Greek poet, to him he fails. I’ll be sworn he knows not so much as one character of the tongue.” RIC: “Why, then its Greek to him.”
IT WAS LATER used by Shakespeare in “Julius Caesar in 16:16. He has CASSIUS saying: “Did Cicero say anything?” To which CASCA responded: “Ay, he spoke Greek.” CASSIUS then ask: “To what effect?” CASCA answered: “Nay, an I tell you that, I’ll ne’er look you in 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.”
Thus, the expression is used now days in referring to that in which we do not understand.
Dub Mowery is a Gospel preacher in the Church of Christ. A native of Southeast Oklahoma, he is the author of Colloquial Sayings & Expressions (Morris Publishing, 2008)