Origins
The word 'rose' is one of the great wandering loanwords of Western civilization — a word that followed its referent along trade routes from ancient Iran through Greece and Rome into the languages of modern Europe. English 'rose' comes from Old English 'rōse,' an early borrowing from Latin 'rosa' (rose). Latin 'rosa' was borrowed from Greek 'rhódon' (ῥόδον, rose), and the Greek word is widely believed to derive from Old Iranian *wṛda- (rose, flower), attested in Avestan 'varəda-' and reflected in Armenian 'vard' (rose) and Arabic 'ward' (rose, borrowed from Persian).
The Iranian origin aligns with the horticultural history. Roses were cultivated in Persia millennia before they reached the Mediterranean. The ancient Persians developed sophisticated rose gardens and extracted rose water and rose oil ('attar of roses'), technologies that later spread westward. The word and the cultivation moved together — a linguistic migration that mirrors a botanical one.
The Greek form 'rhódon' appears in two prominent English words. 'Rhododendron' means literally 'rose tree' (rhódon + déndron, tree) — the rhododendron was named for its rose-like flowers. The island of Rhodes ('Rhódos') was traditionally known as the 'rose island,' whether because roses grew abundantly there or because the name was folk-etymologized to connect with the Greek rose-word.
Latin Roots
The Latin 'rosa' generated an enormous family in the Romance languages and in English. A 'rosary' (Latin 'rosārium') was originally a rose garden; the devotional meaning arose from the medieval metaphor of prayers as roses — each prayer was a rose offered to the Virgin Mary, and the complete cycle of prayers was a garland or garden of roses. 'Roseate' means rose-coloured or optimistic. A 'rosette' is a rose-shaped ornament. 'Sub rosa' (under the rose) means 'in secret' — from the ancient custom of hanging a rose above a meeting table to indicate that all discussions were confidential. The rose's association with secrecy is ancient, possibly connected to the myth of Harpocrates, the Greco-Egyptian god of silence, who was depicted with a rose.
'Rosemary' appears to contain 'rose' but actually does not — it comes from Latin 'rōs marīnus' (sea-dew), referring to the plant's coastal habitat. The folk-etymological reshaping to 'rose-mary' is a false connection, though it has influenced the plant's cultural associations with both roses and the Virgin Mary.
The War of the Roses (1455-1487) between the Houses of Lancaster (red rose) and York (white rose) made the rose the most politically charged flower in English history. The Tudor rose, combining red and white, symbolized the union of the warring houses. Shakespeare's line 'A rose by any other name would smell as sweet' (Romeo and Juliet, II.ii) has become perhaps the most famous statement about the arbitrary relationship between words and things — ironically delivered about a flower whose very name has travelled through four languages and three millennia.