Eager is wanting to start so badly that you can hardly sit still. A dog by the front door with the lead already in its mouth; a child awake at six on the first morning of the holiday.
Two patterns carry it: eager TO do something and eager FOR something. Eager to please describes a person who bends over backwards to be liked, and an eager young reporter is the stock phrase for someone new and keen. The adverb turns up in one phrase above all others — eagerly awaited. Keen means much the same and sounds more everyday in British English, so eager is the slightly literary choice. Do not confuse it with anxious: an eager traveller cannot wait to go, while an anxious one is worrying about it.
1adjectiveeagerFull of impatient excitement about doing or getting something.
“The students were eager to start the experiment.”
synonyms: keen, enthusiastic
2adjectiveshowingShowing strong desire or anticipation.
“A row of eager faces looked up from the front bench.”
Also accepted in games: keen
Eager came through Middle English egre from Old French aigre, and behind that stands Latin ācer, "sharp, keen". The same French word is still in your kitchen cupboard: vinegar is vin aigre, sour wine. English kept the sharpness of the word and left the sourness behind.
Proto-Indo-European
*h₂eḱ-
Middle English
egre
English, today
eager
Built from
From Middle English egre. Middle English egre, eger, from Old French aigre, egre (modern aigre), from Latin ācrus, variant of ācer (“sharp, keen”); see acid, acerb, etc. Compare vinegar, alegar.
Etymology from Wiktionary, CC BY-SA