eager

The journey of 'eager' begins with the Proto-Indo-European root h₂eḱ-, which conveyed the fundamental concept of sharpness. This root gave rise to the Latin adjective ācer, which carried both a physical sense ('sharp to the touch, pungent to the taste') and a figurative one ('keen, fierce, spirited'). Through Old French aigre, meaning 'sharp, sour, keen', the word entered Middle English. Over time, the English meaning specialized, shedding the primary physical senses of sharpness and sourness to focus almost exclusively on the figurative intensity of keen desire or enthusiastic impatience. Thus, the modern abstract meaning of ardent enthusiasm evolved directly from the ancient metaphor of mental or emotional 'sharpness'.

The word is a simplex form. It entered English from Anglo-Norman French egre or Old French aigre, meaning 'keen, sharp, sour'. This, in turn, derives from Latin ācer, ācris, meaning 'sharp, pungent, eager, fierce'. The ultimate origin is Proto-Indo-European h₂eḱ- ('sharp').