keen-eyed

The compound 'keen-eyed' is a transparent English formation that directly combines two native elements. The adjective 'keen' evolved from an Old English term for bravery to its modern sense of sharpness, particularly of the mind or senses. The second element, 'eyed', is derived from the Old English noun for the organ of sight, combined with a common adjectival suffix. The logic of the word is perfectly literal: possessing eyes that are metaphorically 'sharp' or acute, leading to the modern meaning of being highly observant and visually perceptive. This compound exemplifies how English can create vivid descriptive terms by combining simple, concrete concepts.

Structure: keen (sharp) + eyed (having eyes) - keen: From Old English cēne (brave, bold, fierce), later developing the sense of 'sharp' (as in a blade or intellect). In this compound, it functions as an intensifier meaning 'sharp' or 'acute'. - eyed: From Old English ēage (eye) + the suffix -ed, used to form adjectives meaning 'having (a specified kind of) eyes'.