Origins
The word 'corner' belongs to one of the most prolific and far-reaching etymological families in the Indo-European languages — the family of the horn. Its journey from animal anatomy to architectural geometry is a vivid example of how concrete body-part metaphors shape the vocabulary of abstract space.
English borrowed 'corner' from Anglo-Norman French 'cornere' in the late 13th century. The Anglo-Norman word derived from Old French 'corne,' meaning 'horn' and, by extension, any pointed projection or angle. Old French 'corne' descended from Latin 'cornu,' one of the most versatile nouns in the classical vocabulary. In Latin, 'cornu' meant the horn of an animal, the wing of an army (which projected outward like a horn), the tip of a crescent moon, the arm of a bay, a mountain peak, and the hard material horn itself.
Latin 'cornu' traces back to Proto-Indo-European *ḱerh₂-, a root meaning 'horn' or 'head.' This root produced an enormous family of descendants across the Indo-European languages: Greek 'keras' (κέρας, horn — as in 'rhinoceros,' meaning 'nose-horn,' and 'triceratops,' meaning 'three-horn-face'), Sanskrit 'śṛṅga' (horn, peak), Welsh 'carn' (cairn, horn), and the Germanic words for horn — Old English 'horn,' German 'Horn,' Old Norse 'horn' — all from the same source.
Latin Roots
The semantic path from 'horn' to 'corner' is intuitive once laid bare. A horn is a hard, pointed projection. Where two walls meet, they form a pointed projection — a horn-like angle. Latin already used 'cornu' this way: the 'cornua' of a building were its projecting angles. French extended this into the dedicated noun 'cornere' for the angle where surfaces meet, and English adopted it.
What is linguistically interesting is that English already had a native word for this concept: 'nook,' from Middle English 'nok,' of Scandinavian origin. But 'corner' and 'nook' came to occupy different semantic niches. A corner is sharp, geometric, and often public (a street corner, a corner office), while a nook is sheltered, curved, and private (a breakfast nook, every nook and cranny). The French-derived word took the angular, exposed sense; the Norse-derived word kept the cozy, enclosed one.
The Latin 'cornu' family gave English an extraordinary range of vocabulary. 'Cornet' (from Old French 'cornet,' literally 'little horn') was originally a small brass horn and later transferred to the paper cone shaped like a horn used to hold sweets. 'Cornucopia' (from Latin 'cōpiae cornu,' horn of plenty) refers to the mythical horn of the goat Amalthea, which Zeus broke off and which thereafter produced endless food. 'Unicorn' (from Latin 'ūnicornis,' one-horned) names the legendary beast. 'Corn' in the podiatric sense — a hard growth on the toe — comes from Latin 'cornu' via French, because the callused skin is as hard as horn.
Middle English
The expression 'to corner' someone, meaning to drive them into a corner from which they cannot escape, dates from the early 19th century. 'To corner the market' — to buy up enough of a commodity to control its price — is an American English metaphor from the 1830s, probably from the image of driving something into a corner. 'Cornerstone,' the first stone laid at the corner of a building's foundation, is attested from the 13th century and rapidly became a metaphor for anything fundamental.
In sports, the corner has generated its own vocabulary: a corner kick in football, a corner in boxing (where a fighter's team waits between rounds), fighting out of the corner, and cutting corners (originally a racing term for taking the inside line of a turn, later generalized to mean taking shortcuts). Each of these preserves the spatial sense of a meeting point of two lines.
The Germanic cognate 'horn' traveled its own parallel path in English. A horn can be a musical instrument, a part of a car, an animal's weapon, or a geographical feature (Cape Horn, the Golden Horn of Istanbul, the Horn of Africa). The branching of 'horn' into the full, native English sense and 'corner' into the borrowed Anglo-Norman sense is a typical example of the lexical enrichment that occurred when French vocabulary layered onto the Anglo-Saxon substrate after 1066.
Modern Usage
What makes 'corner' especially revealing is how thoroughly the horn metaphor disappeared from conscious awareness. No English speaker today thinks of a street corner as a horn — yet the image is preserved in the word itself, a fossil metaphor carried forward across three thousand years of linguistic change from Indo-European pastures to modern city grids.