What is an Ide anyway, and why should I be scared of it?
In Roman days, dates were calculated by counting back from three fixed points: Kalendae, the first day of a month (and the origin of the word calendar); Nonae, between the fifth and seventh days of a month; and Ides, between the 13th and 15th days of the month, and specifically on 15 March. Or today, in other words. These dates are believed to have been based on the phases of the moon. Kalendae was probably originally based on the first day of a new moon, Ides a full moon, and Nonae a half moon.
So, should you be worried today? Not really. The day had long been a day of religious observation in Ancient Rome (originally to celebrate the New Year, as the oldest Roman calendar began in March), but became infamous when Julius Caesar was assassinated on that date. Which was significant not just for the assassination for the man who at the time Dictator Perpetuo (Dictator in Perpetuity) of the Roman Republic, but for the fact that the assassination was one of the key events in the end of the Roman Republic and the riseof the Roman Empire.
Caesar actually contributed quite a bit to the English language. The phrase to cross the Rubicon, meaning to pass a point of no return, refers to his decision to march across the Rubicon River, in an act of defiance after he had been ordered to return to Rome. He may also have said Alea iacta est (The die is cast) as they crossed the river. And a few years before then, after a short and decisive victory at the Battle of Zela, he apparently uttered the following in the Senate: Veni, vidi, vici (the pithy I came, I saw, I conquered, which is even pithier in the origin Latin).
The most common word directly inspired by Caesar is July. The month was named after him as it was the month of his birth. Which I think officially makes you A Big Deal. (August was named after his grandnephew and adopted son Gaius Octavian, later known as Caesar Augustus).
And of course there’s Et tu, Brute? which comes from Shakespeare’s play Julius Caesar. Caesar’s last words before his death in the play, they express shock at the involvement of his friend Marcus Brutus, and are still used today (usually somewhat ironically) to express disappointment in a similar betrayal. There’s no evidence that Caesar actually said this though, so it’s probably entirely Shakespeare’s invention.
And most sadly for Caesar, he had nothing to do with the Caesar Salad, which is named after Caesar Cardini, the Italian immigrant restaurateur who created it and served it in his restaurants in the US.
So while Julius Caesar probably never said Et tu, Brute? or wowed his friends with his new salad, he would still probably be fairly satisfied with his contribution to the English language. Once he got over the fact that no-one speaks Latin anymore.