Origins
The word 'crown' entered English from Anglo-Norman 'coroune' in the twelfth century, but its roots reach back through Latin to ancient Greek, and its semantic history traces the evolution of a symbol from humble vegetable wreath to the supreme emblem of sovereignty.
The Latin source is 'corōna,' meaning 'wreath, garland, crown.' In Roman culture, a 'corōna' was primarily a wreath of leaves, flowers, or grass awarded for achievement — military valor, athletic victory, or civic distinction. The 'corōna cīvica' (civic crown, made of oak leaves) was one of the highest military decorations, awarded to a soldier who saved the life of a fellow citizen in battle. The 'corōna triumphālis' (triumphal crown, of laurel) was worn by a victorious general during his triumph. Only later was 'corōna' applied to the metal diadems of emperors and kings, which borrowed both the circular form and the name of the earlier vegetable crowns.
Latin 'corōna' was borrowed from Greek 'korṓnē' (κορώνη), which had the general meaning of 'anything curved or hooked.' The word also meant 'a crow' — the bird with the curved beak — and 'the curved end of a bow.' The semantic thread connecting all these meanings is curvature: a crown is a curved band encircling the head, just as a korṓnē is any curved thing.
Middle English
The phonological journey from Latin 'corōna' to English 'crown' involved several stages. Old French 'corone' preserved the Latin form fairly closely. Anglo-Norman 'coroune' added the typical Norman vocalization. Middle English forms included 'coroune,' 'coroun,' and 'crowne,' the last showing the collapse of the unstressed middle vowel and the development of the /aʊ/ diphthong that characterizes the modern pronunciation.
The Latin word 'corōna' produced an extraordinarily productive family of English derivatives. 'Coronation' (the ceremony of crowning a monarch) comes from Medieval Latin 'corōnātiō.' 'Coronary' (pertaining to the crown, especially the coronary arteries that encircle the heart like a wreath) comes from Latin 'corōnārius.' 'Coroner' is a remarkable case: the original form was Anglo-Norman 'corouner' (literally 'crowner'), an officer of the crown whose job was to protect the financial interests of the monarchy — investigating deaths that might involve royal revenue, such as cases of treasure trove, forfeiture, or deodand. The coroner's role gradually shifted from fiscal to judicial, becoming the medical-legal examiner we know today, but the word still carries the crown in its etymology.
'Corolla' (the ring of petals in a flower) is a Latin diminutive of 'corōna' — literally 'a little crown.' 'Corollary' (something that naturally follows, an additional result) comes from 'corōllārium,' originally a money gift for buying a garland — a bonus, something extra that comes along with the main thing.
Latin Roots
The word 'corona' itself was borrowed directly into English from Latin, maintaining its scientific and technical senses. The solar corona (the luminous halo visible during a total eclipse) was named for its resemblance to a crown. The coronavirus family received its name in 1968 because the virus particles, viewed under electron microscopy, display a fringe of bulbous projections that resembles a crown or solar corona.
Several European currencies take their name from 'corōna': the Swedish 'krona,' the Norwegian and Danish 'krone,' the Czech 'koruna,' and the former Austro-Hungarian 'Krone' all mean 'crown,' reflecting the practice of stamping a crown on coins as a symbol of royal authority. The English crown coin (worth five shillings) was minted from the reign of Henry VIII until decimalization in 1971.
The metaphorical extension of 'crown' to mean 'the top of something' (the crown of the head, the crown of a hill, the crown of a tooth) is ancient, attested in Latin. In each case, the crown is conceived as the highest point, the summit — just as the crown sits at the top of a monarch's body, marking the apex of the social hierarchy. The phrase 'crowning achievement' captures this perfectly: the best accomplishment is the one that sits on top of all the others, like a crown on a head.