hour

hour mid-13c., from O.Fr. hore "one-twelfth of a day" (sunrise to sunset), from L. hora "hour, time, season," from Gk. hora "any limited time," from PIE *yor-a-, from root *yer- "year, season" (see YEAR (Cf. year)). Greek hora was "a season; 'the season;'" in classical times, sometimes, "a part of the day," such as morning, evening, noon, night. The Greek astronomers apparently borrowed the notion of dividing the day into twelve parts (mentioned in Herodotus) from the Babylonians (night continued to be divided into four watches), but as the amount of daylight changed throughout the year, the hours were not fixed or of equal length. Equinoctal hours did not become established in Europe until the 4c., and as late as 16c. distinction sometimes was made between temporary (unequal) hours and sidereal (equal) ones. The h- has persisted in this word despite not being pronounced since Roman times. Replaced O.E. tid, lit. "time," and stund "period of time." As a measure of distance ("the distance that can be covered in an hour") it is recorded from 1785.