Origins
The word 'court' traces one of the most remarkable semantic journeys in English: from a farmyard pen to the highest tribunal in the land.βββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ Its path runs through livestock enclosures, royal audiences, aristocratic manners, and legal proceedings -- all connected by the idea of an enclosed space where important things happen.
The word enters English around 1175 from Old French 'cort' (enclosed yard, royal retinue, place of justice), from Latin 'cohors' (genitive 'cohortis'), whose earliest meaning was 'an enclosed yard or pen' -- a space fenced off for livestock or storage. The word is generally analyzed as a compound of the prefix 'co-' (together) and a root related to 'hortus' (garden, enclosed space), both ultimately from PIE *gher- (to grasp, to enclose).
The semantic development in Latin proceeded in clear stages. First, 'cohors' meant an enclosed yard. Then, by metonymy, it came to mean the group of people enclosed within such a yard -- a company, a retinue. In military usage, a 'cohors' became a specific unit of the Roman army: a cohort, typically about 480 soldiers, one-tenth of a legion. In civilian usage, the word described the retinue or household of a prominent person -- the people who gathered in the enclosed space around a patron or ruler.
French Influence
In the transition to Romance languages, 'cohors' lost its military sense and retained its civilian one. Old French 'cort' meant the yard or residence of a lord, the group of people around a lord, and -- because lords administered justice from their residences -- the place where legal cases were heard. English 'court' inherited all three senses: a physical space (courtyard, tennis court), a social body (the royal court), and a legal institution (a court of law).
The PIE root *gher- (to grasp, to enclose) connects 'court' to a wider family of enclosure words. Latin 'hortus' (garden) descended from it directly, and through French produced English 'orchard' (though this blended with Old English 'orceard'). Frankish *gardo (enclosure, garden), from the same PIE root through Germanic, entered French as 'jardin' and English as 'garden.' Greek 'khortos' (enclosure, feeding place, fodder) is cognate, and the English word 'yard' descends from Old English 'geard' (enclosure), from the same PIE root through Germanic. So 'court,' 'garden,' 'yard,' and 'orchard' are all descendants of the same ancient word for an enclosed space.
The derivative 'courtesy' (from Old French 'cortesie,' behavior befitting a court) reveals the social dimension: courteous behavior was originally the refined conduct expected in a royal court. 'Courtier' (one who attends a court), 'courtship' (the wooing behavior of courtiers, extended to romantic pursuit), and 'courtesan' (a court woman, later a high-status prostitute) all derive from the same root, tracing the social life that unfolded within the enclosed space of the royal court.