Other forms: eves
The eve of something is the day or evening before it. Christmas Eve, New Year's Eve, on the eve of the election.
It takes a capital letter in the named ones and lower case elsewhere. The figurative use is common in journalism — on the eve of a decision, on the eve of war — and it always suggests something significant about to happen. The word is a shortened form of even, meaning evening, which survives in eventide and in the poetic even. Note that eve is also a name, and that the two have nothing to do with each other.
1nouneveThe day or evening before a special day.
“The shops shut early on Christmas Eve.”
2nountimeThe time just before an important event.
“It was announced on the eve of the vote.”
Too few real examples of this word to estimate which sense is commonest.
eve is a time just before.
Old English aefen meant evening. The final n dropped away in the phrase Christmas even, leaving Christmas Eve, and the shortened form then became a word of its own — a rare case of a word created by wearing another one down inside a single phrase.
Old English
ǣfen
English, today
eve
Built from
From a variant of the Middle English - noun even (itself from Old English ǣfen), with a pre-1200 loss of the terminal '-n', which was mistaken for an inflection. See also the now archaic or poetic even (“evening”), from the same source. In medieval Europe, days were considered to extend from sunset to sunset rather than midnight to midnight, so the night before a holiday was considered part of it, hence its "eve".
Etymology from Wiktionary, CC BY-SA