We don’t know where the word Ides comes from or why the Ancient Romans used plural words for singular dates. Thanks, Caesar.
Today is the Ides of March, when Julius Caesar was notoriously assassinated in 44BC. Shakespeare immortalized the date when his soothsayer warned in The Tragedy of Julius Caesar: “Beware the ides of March” (1.2.19). Both of these are true: Caesar was killed on March 15 and a seer, according to ancient historians, did caution him the Roman ruler about the date, though didn’t exactly say Shakespeare’s famous words. But why is this day called the Ides and if it’s just one day, why don’t we call it an Ide?
The tides of Ides
The Ancient Roman calendar had three major days: The Kalends marked the first of the month, the Nones the 5th or 7th depending on the month’s length, and the Ides the 13th or 15th. For March, as we know, the Ides fell on the 15th. Originally, this mid-month milestone would have corresponded to the full moon.
Kalends, from Kalendae, is rare instance of an archaic K in Latin. Kalendae appears to be related to the verb calare, “to call out.” On this day, after they observed the new moon, priests declared the number of days until the Nones and Ides. Just as we often pay our bills on the first of the month, so the Ancient Romans settled their accounts on the Kalends, hence calendarium, “an account book,” leading to our word calendar.
Nones comes from Nonae, the plural of nonus, “ninth.” The Nones fell eight days before the Ides, but the Romans counted their days inclusively, adding the target Ides to make nine. Our word noon is directly related to nonus: It comes from hora nona, the “ninth hour” of daylight. This was around 3pm for the Ancient Romans – and Anglo-Saxons, when the Church first borrowed the term, fully shifted to today’s 12pm either due to a customary midday meal or prayer time by the 14th century. The English nine also shares a deeper Indo-European root with nonus.
In some instances, the accusative case of these words were used when recording dates. For Kalendae, this was Kalendas, Nonae Nonas, which helps explain why English used Kalends and Nones.
As for Ides, it comes from the Latin Idus, rendered as Eidus. We simply don’t know where this word comes from. Eidus points to an Oscan form of Ides; a sister to Latin , the long-extinct Oscan was spoken southeast of Rome. The best guess scholars have is that Ides comes from some lost Etruscan word, perhaps meaning “to divide,” as the full moon so organized their months.
But why do we refer to a singular date – March 15 – as Ides and not Ide? At points in English, we sometimes did, but this technically breaks with history. The Ancient Romans always used plural forms for these dates. As Agnes Kirsopp Michels notes in The Calendar of the Roman Republic:
It is an interesting fact that in Latin and Greek the names of regularly recurring days are often plural, as are many of the annual religious observances which give names to calendar days.
Perhaps the fact of their recurrence lent a sense of plurality? Or perhaps plurality better accorded with the religious significance of these days?
But, Michels continues: “Why this should be true of some days and not of others is a puzzle.”