late 14c., "clock-maker," via Latin from Greek hōrologe "clock, timepiece, instrument for measuring the hours of a day," from hōrologos "telling the hour," from hōra "hour" (see hour) on model of astrologer, etc. Hence also obsolete English horologe "timepiece, sundial, hourglass, clock, cock" (late 14c.) and the old expression the devil in the horologe for "mischief in an orderly system" (17c.).
Entries linking to horologer
c. 1200, "divine office prescribed for each of the seven canonical hours; the daily service at the canonical hours;" c. 1300, "time of day appointed for prayer, one of the seven canonical hours," from Old French ore, hore "canonical hour; one-twelfth of a day" (sunrise to sunset), from Latin hora "an hour;" poetically "time of year, season," from Greek hōra a word used to indicate any limited time within a year, month, or day (from PIE *yor-a-, from root *yer- "year, season;" see year).
Church sense is oldest in English. Meaning "one of the 24 equal parts of a natural solar day (time from one sunrise to the next), equal hour; definite time of day or night reckoned in equal hours," and that of "one of the 12 equal parts of an artificial day (sunrise to sunset) or night, varying in duration according to the season; definite time of day or night reckoned in unequal hours" are from late 14c. In the Middle Ages the planets were held to rule over the unequal hours. As late as 16c. distinction sometimes was made in English between temporary (unequal) hours and sidereal (equal) ones. Meaning "time of a particular happening; the time for a given activity" (as in hour of death) is mid-14c.
The h- has persisted in this word despite not being pronounced since Roman times. Replaced Old English tid, literally "time" (see tide (n.)) and stund "period of time, point of time, hour," from Proto-Germanic *stundo (compare German Stunde "hour"), which is of uncertain origin. German Uhr likewise is from French.
Greek hora could mean "a season; 'the season' (spring or summer)." In classical times it sometimes meant "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 (see watch (n.)); but because the amount of daylight changed throughout the year, the hours were not fixed or of equal length.
As a measure of distance ("the distance that can be covered in an hour") it is recorded from 1785. At all hours "at all times" is from early 15c. For small hours (those with low numbers) see wee (adj.).
Narrowed meaning "one who professes to determine the influence of planets on persons and events" is from c. 1600, however during the early Modern English period when astrologer and astronomer began to be differentiated, "the relation between them was at first the converse of the present usage" [OED]. Shakespeare used astronomer where we would write astrologer.