originally the designation given to an Indian infantryman armed with a musket in the armies of the Great Mogul.
In the 18th century the French East India Company and its other European counterparts employed locally recruited soldiers within India, mainly consisting of infantry designated as "sepoys". The largest of these Indian forces, trained along European lines, was that belonging to the British East India Company.
The term "sepoy" is still used in the modern Nepalese Army, Indian Army and Pakistan Army, where it is used for the rank of private soldier.
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A little further up the road Dawson himself was lying on his face, quite dead, with an empty revolver in his hand and four Sepoys lying across each other in front of him.
Arthur Conan Doyle. Sherlock Holmes: The Sign of the Four
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he who had blown a considerable number of sepoys from the cannonmouth without flinching, could not now restrain his natural emotion.