More than a tick of sixty minutes
In present-day English an hour is one twenty-fourth of a day, sixty minutes on a clock. The same noun also names a slot in the day, a stretch of paid work, a stretch of road, and, in church language, a fixed time of prayer. That last use is not a late extra. It is close to how the word first behaved once it entered English.
The origin of the word hour is a borrowing, not a native Germanic coinage. When it arrived, it began to crowd out older English words for a span of time.
A French loan with a church job
Middle English took the noun from Old French, where forms such as ore, hore, houre, and ure could mean a canonical hour or one twelfth of the period from sunrise to sunset. Those French forms go back to Latin hora, which Latin had taken from Greek hōra.
The earliest English record belongs to the thirteenth century. Dictionaries that date the church sense put it around 1200; the first firmly cited evidence is before 1250, in the Ancrene Riwle. In those early uses the word meant the daily offices prescribed for the canonical hours, and soon afterward the appointed time of day for those prayers. Only toward the late fourteenth century does it settle as a regular division of the natural day.
Old English already had words for a portion of time. Tīd, the ancestor of modern tide, could mean a point or period of time, a season, a feast day, even a canonical hour. Stund, later stound, meant a span or a point of time; German Stunde, still the ordinary word for the clock unit in that language, belongs to the same Germanic family. Hour did not grow out of those native terms. It replaced them for the clock measure, while tide kept other work, including the rise and fall of the sea.
A seasonal span before it was a numbered slice
Latin hora could mean an hour, but in verse it also meant a season or a time of year. Greek hōra was broader still: any bounded stretch within a year, a month, or a day. It could name a season, especially the fair part of the year; a time of day such as morning or noon; youth as a time of life; or the right moment for something. The narrow sense of a numbered hour is later and more technical.
Greek astronomers treated daylight as twelve parts. That scheme is often linked to Babylonian practice; Herodotus already mentions a twelve-part day. Because daylight itself lengthens and shortens through the year, those twelve parts were not constant. Night, in much of the ancient Mediterranean, was still counted in watches rather than in the same equal slices.
Reconstructions of the deeper root vary in notation. One standard handbook traces the Greek noun to a Proto-Indo-European root written yēr-, with the sense year or season. Other etymological dictionaries reconstruct a related form for year and season. Either way, the same family includes English year and German Jahr. Hour and year are distant cousins, not parent and child: one came through Greek and Latin, the other through Germanic inheritance. A later learned borrowing of the Latin noun, hora, sits closer to the French loan.
The initial h in the English spelling is a fossil. The letter has been kept even though the sound has not been heard in this word since Roman times. Modern English still writes hour and says it without the h, which is why the indefinite article before it is an, not a.
Romance cognates stay close to the Latin shape: French heure, Italian ora, Spanish and Portuguese hora. German Uhr, the word for a clock and for o’clock, is another French loan, not the native Stunde. Irish uair and Welsh awr show the same Latin-Greek line reaching the Celtic languages. Related English formations such as hourly and the older adjective horary keep the Latin stem in view without changing the simple noun.
From prayer time to clock time
Meaning in English widened after the church use. By the mid-fourteenth century the word could mean the time of a particular event, as in the hour of death. Late in that century it named both kinds of day-division then in play: twenty-four equal parts of the solar day, and twelve unequal parts of daylight or of night, whose length changed with the season. Medieval planetary hours were counted on that unequal grid. As late as the sixteenth century, English could still distinguish temporary, unequal hours from sidereal, equal ones. The equal hour of the clock won.
Later extensions are thinner but real. The phrase at all hours is recorded from the early fifteenth century. As a measure of distance, the space that can be covered in an hour, the noun appears in the late eighteenth century. School hours, working hours, and military style such as 1300 hours keep it as a label for a scheduled block rather than a pure duration.
Stories that derive the English word from the Egyptian god Horus do not match the documentary path. The trail is Indo-European, through Greek, Latin, and French, not a later Afroasiatic loan.
The silent letter and the German split
The most telling leftover is not a lost sense but a spelling, and a fork in what neighboring languages did with the same loan. English kept the h that Latin writing had, long after the sound had gone, and it kept a church word that had first meant a prayer time rather than a tick of sixty minutes. German speakers, facing the same French loan, used it for the clock face and kept their old native word for the span. English did the opposite: it let tide and stound recede, and let the borrowed noun become the ordinary name of the unit.