The noun ωρα (hora) describes a time interval of indefinite length but natural manifestation (years, months, days, but not centuries and millennia). It comes from the Proto-Indo-European root "yer-" from which we get our word "year" and was also adopted into English as the word "hour"; that's twice the same word, both times meaning "a certain stretch of time". Actually, our Greek word ωρα (hora) describes any cycle of time that can be clearly observed in nature: a year, season, month, day and even the parts of a day that are observable: morning, noon, afternoon, evening. Since an hour is largely arbitrary, our Greek word didn't mean "hour" in the sense of sixty minutes, but rather as arbitrary marker to indicate how far the actually observable cycle (the day) had progressed. In other words: the third hour was mark number 3 on the dial but not the time span between marks 2 and 3.

Contrary to the word χρονος (chronos), which referred to longer periods of time, our noun ωρα (hora) was mostly used to indicate specific points in a temporal cycle. Hence bedtime was known as the hour of going to bed. Since all business occurred during the day, for ordinary people the day had twelve hours but the night did not (John 11:9) In the second century BC, an astronomer called Hipparchus had begun to also divide the night into 12 hours, but that was largely a theoretical endeavor and only useful for astronomers. Preceded by the preposition προς (pros), which describes a motion toward, the idiom "approaching an hour" or rather "a little while" was formed.

Our word in plural may denote any string of cycles but is used proverbially to indicate the seasons and particularly spring. Since spring was associated with blushing youth, the word ωρα (hora) acquired a connotation of loveliness. In Greek mythology, the Horae were lush female deities in charge of the seasons.

The noun ωρα (hora) is used 107 times in the new testament, see full concordance, and from it derive:

In the classics an identical noun ωρα (ora) appears, which doesn't seem to be used independently in the New Testament, but, combined with the adjective ολιγος (oligos), few or little, is part of the verb ολιγωρεω (oligoreo), meaning to give little heed (Hebrews 12:5 only). It's unclear where this noun ωρα (ora) came from, but Liddell and Scott (A Greek-English Lexicon) suggest it derives from a lost word χωρα (chora) or χωρια (choria), a watching or watch-keeping stint, which would bring it in proximity of our noun ωρα (hora), as indicator of time (as in 'the "third watch" of the night'). The opposite of ολιγωρεω (oligoreo), to care little, is πολυωρια (poluoria), to care a lot. This latter word is not used in the New Testament.