/sæʃ/
[noun] A long strip or band of cloth worn around the waist or over one shoulder, often as part of a uniform or as a decoration. It can also refer to the sliding frame that holds the glass in a window.
A 'sash' was once a turban — English speakers heard the Arabic plural 'shāshāt' and thought it was a single word.
The word 'sash' takes two very different paths to reach us, and the more colourful of the two begins in the Arabic-speaking world. The Arabic word 'shāsh' referred to a length of fine muslin cloth, the kind wound around the head to form a turban. When merchants and travellers from the Ottoman Empire encountered Europeans — particularly in trade and military contexts during the 16th century — they used the plural form 'shāshāt' to describe these cloths. English speakers, hearing this unfamiliar plural ending, simply adopted the whole word as if it were a singular noun, producing 'shash' and eventually 'sash.' This process, where a foreign plural is mistaken for a singular, is called a back-formation and has given English several other exotic-sounding words.
The cloth itself was imported along trade routes that ran through Turkey, the Levant, and Egypt, and for some time 'sash' in English specifically meant a strip of fine muslin worn wrapped around the head or the body in what writers of the day considered an 'Eastern' fashion. By the early 17th century, the word had shed its strictly foreign character and began to describe any decorative band of cloth — worn at the waist, across the chest, or over the shoulder. Soldiers wore sashes to indicate their rank or regiment; beauty queens, as we know them today, wear them to announce their title. The cloth had migrated from the head to the body, but the word stayed.
By the time the word was firmly established in English, its military associations were growing strong. Officers in the armies of Britain and continental Europe wore silk sashes, often in vivid regimental colours, tied around the waist or draped diagonally across the torso. This gave 'sash' a sense of ceremony and status that pure Arabic 'shāsh' — practical turban-cloth — had never quite carried. Language often elevates the things it borrows, and 'sash' is a perfect example: a humble strip of woven fabric became a symbol of honour and achievement.
The second meaning of 'sash' — the sliding window frame — has a completely separate origin, though the two meanings have coexisted so long that most speakers never question the connection. The window 'sash' most likely comes from the French word 'châssis,' meaning a frame or chassis, which itself derives from the Old French 'chasse,' meaning a case or frame, rooted in the Latin 'capsa,' meaning a box or container (the same Latin root that gives us English 'case' and 'capsule' via the chain Latin capsa → Old French chasse → Old French châssis → English sash). English borrowed 'châssis' in the 17th century, at precisely the time when the sliding sash window was becoming fashionable in British architecture, and the word was shortened and altered until it sounded identical to the cloth word.
What makes 'sash' so delightful as a piece of linguistic history is the way two completely unrelated words — one Arabic, one French — collapsed into a single four-letter sound without anyone noticing. Speakers today who pull up a sash window and tie a sash around their waist at a school prize-giving are using two words with entirely different ancestors, connected only by accident of sound. English is full of these quiet collisions, where history has pressed two stories into one short syllable.