c. 1200, "a day as reckoned back from the first of the following month" (as fourteenth calend of March = February 16th), from Latin kalendae "first day of the month" in the Roman calendar (see calendar). It is attested in English from mid-14c. as "the first day of the month," and from late 14c. as the beginning of anything.
updated on October 30, 2022