hourlong (adj.)

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.).

Old English lang "having a great linear extent, that extends considerably from end to end; tall; lasting," from Proto-Germanic *langa- (source also of Old Frisian and Old Saxon lang, Old High German and German lang, Old Norse langr, Middle Dutch lanc, Dutch lang, Gothic laggs "long").

The Germanic words perhaps are from PIE *dlonghos- (source also of Latin longus "long, extended; further; of long duration; distant, remote," Old Persian darga-, Persian dirang, Sanskrit dirghah "long"), from root *del- (1) "long" (source also of Greek dolikhos "long," endelekhes "perpetual"). Latin longus (source of prolong, elongate, longitude, etc.) thus is probably cognate with, but not the source of, the Germanic words. The word illustrates the Old English tendency for short "a" to become short "o" before -n- (also retained in bond/band and West Midlands dialectal lond from land and hond from hand).

Also in Old English in reference to time, "drawn out in duration," with overtones of "serious." The old sense of "tall" now appears to be dialectal only, or obsolete. For long "during a long time" is from c. 1300. To be long on something, "have a lot" of it, is from 1900, American English slang. A long vowel (c. 1000) originally was pronounced for an extended time. Mathematical long division is from 1808. Sporting long ball is from 1744, originally in cricket. Long jump as a sporting event is attested from 1864. A long face, one drawn downward in expression of sadness or solemnity, is from 1786. Long in the tooth (1841 of persons) is from horses showing age by recession of gums (but not in this sense until 1870). Long knives, name Native Americans gave to white settlers (originally in Virginia/Kentucky) is from 1774, perhaps a reference to their swords. Long time no see, supposedly imitative of American Indian speech, is first recorded 1919 as Chinese English.