Origins
The English adjective 'round' is one of the most fundamental shape words in the language, yet it is not native to English. It was borrowed from Old French 'ront' (later 'rond') around 1290, displacing the Old English word 'sinwealt' (round, cylindrical), which has left no trace in Modern English. The French word descended from Vulgar Latin *retundus, an altered form of Classical Latin 'rotundus' (round, circular, spherical), itself derived from 'rota' (wheel), from the PIE root *ret- meaning 'to run' or 'to roll.'
The etymological heart of 'round' is the wheel. Latin 'rota' was one of the most culturally significant words in the ancient world, naming the technology that transformed human civilization. From 'rota' came 'rotare' (to turn), producing English 'rotate,' 'rotary,' 'rotor,' and 'rotunda.' The adjective 'rotundus' (wheel-shaped, circular) gave both 'round' (through French) and 'rotund' (borrowed directly from Latin in the fifteenth century, now meaning 'plump'). The two words are etymological doublets — the same Latin word borrowed twice through different channels.
The displacement of Old English 'sinwealt' by French 'round' is a striking example of lexical replacement following the Norman Conquest. 'Sinwealt' was a compound of 'sin-' (perpetual, continuous) and 'wealt' (rolling), meaning something that rolls perpetually — a wheel, a sphere, anything circular. It was a perfectly good word, transparent in meaning and well-established in the language. But the prestige of Norman French and the cultural dominance of French-speaking aristocracy gradually drove it out of use. By the fourteenth century, 'round' was the standard term, and 'sinwealt' was extinct. Few cases illustrate more clearly how political conquest can reshape even the most basic vocabulary of a language.
Middle English
The Old French form 'ront' shows a characteristic sound change from Latin to French: the loss of the intervocalic 'd' in 'rotundus' and the nasalization of the vowel before 'n.' The spelling 'rond' (with a 'd') was a later restoration influenced by awareness of the Latin original. English borrowed the word in its round (pun intended) Middle English form 'round' or 'rounde,' adding a 'd' that French itself had only recently restored.
In Modern English, 'round' is one of the most grammatically versatile words, functioning as adjective (a round table), noun (a round of drinks), verb (to round a corner), adverb (come round), and preposition (round the clock). Few English words cross this many part-of-speech boundaries. The noun 'round' alone has an extraordinary range: a round of ammunition, a round of golf, a round of applause, a round in boxing, a musical round (like 'Row, Row, Row Your Boat'). The common thread is circularity or cyclical repetition — things that go around.
'Roundabout' (a circular traffic junction, or an indirect route) dates from the seventeenth century as an adjective and the early twentieth century in its traffic sense (primarily British English; Americans say 'traffic circle' or 'rotary'). 'Surround' appears to contain 'round' but actually derives from Late Latin 'superundare' (to overflow); its current form was reshaped by folk etymology, influenced by 'round.'
Figurative Development
The phrase 'round number' (a number ending in zero, or an approximate figure) dates from the sixteenth century. The metaphor is of a number whose edges have been smoothed away, leaving a clean, circular wholeness — 100 rather than 97, 1000 rather than 1,014. 'Round table' carries Arthurian connotations: King Arthur's Round Table was circular so that no knight could claim precedence, making the shape a symbol of equality. A 'roundtable discussion' preserves this idea.
In music, a 'round' is a composition in which voices enter in succession singing the same melody, creating overlapping harmony — the musical equivalent of circular motion. 'Three Blind Mice' and 'Frère Jacques' are the most familiar examples. This usage dates from the sixteenth century.
The PIE root *ret- (to run, to roll) may also have contributed to other English words through the Germanic branch. 'Roll' itself came into English from Old French 'rolle' (from Latin 'rotula,' diminutive of 'rota'), adding yet another layer to the wheel-round-roll semantic cluster. The German 'rund' (round) was itself borrowed from French, showing that the word's influence extended beyond the Romance-speaking world.