ides (n.)youdaoicibaDictYouDict[ides 词源字典]
(plural) early 14c., "middle day of a Roman month," from Old French Ides (12c.), from Latin idus (plural), a word perhaps of Etruscan origin. The 15th of March, May, July, and October; the 13th of other months. "Debts and interest were often payable on the ides" [Lewis].[ides etymology, ides origin, 英语词源]