It's all Greek to me!
Updated: Oct 5, 2020
In ancient Athens, citizens could vote once a year to get rid of someone they disliked. Each man (as women didn't have a vote in Ancient Greek democracy) would write a name on a piece of broken pottery called an ostracon. The person named the most times was kicked out of the city. Hence our word ostracize, meaning to exclude or banish.
When Theseus entered the Labyrinth to slay the Minotaur, he unravelled a ball of string, known as a clewe, to help him find his way back out of the maze. The word clewe evolved into the word clue, meaning something that helps you find the answer to a problem.
Incidentally, the expression 'It's all Greek to me' was coined by William Shakespeare, who used it literally in his play Julius Caesar. When Seneca deliberately gives a speech in Greek so that some people won't understand it, Casca remarks: "For mine own part, it was Greek to me". It soon became an expression used to mean that something is difficult to understand.