eveningyoudaoicibaDictYouDict[evening 词源字典]
evening: [OE] Evening is a derivative of even [OE], a word for ‘evening’ now restricted to bad poetry. This came ultimately from an Indo- European base, whose general meaning of ‘lateness’ is pointed up by other descendants such as Sanskrit apara- ‘later, western’, Greek opsé ‘late’, and Gothic iftuma ‘following, later’. The specific application to ‘latter part of the day’ seems only to have occurred in the Germanic languages, where it is represented in German abend and Dutch avond, and also possibly in Swedish afton and Danish aften (although these could be from another source).

The Old English word was ǣfen, which formed the basis of a verb ǣfnian ‘become evening’; the verbal noun derived from this has become English evening. Eve [13], as in ‘Christmas eve’, is a Middle English reduction of even.
[evening etymology, evening origin, 英语词源]
evening (n.)youdaoicibaDictYouDict
from Old English æfnung "the coming of evening, sunset, time around sunset," verbal noun from æfnian "become evening, grow toward evening," from æfen "evening" (see eve). As a synonym of even (n.) in the sense "time from sunset to bedtime," it dates from mid-15c. and now entirely replaces the older word in this sense. Another Old English noun for "evening" was cwildtid.