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Uncle Sam,name used to designate the U.S. government. The origins of the term are unclear. The term was believed to have arisen in the War of 1812, when it seems to have been used at first derisively by those opposed to the war, but its use in a navy midshipman's letter of 1810 indicates that it originated earlier, perhaps as naval slang. Possibly it was an expansion of the letters "U.S." on uniforms and government property. Other sources have attributed the origin of the term to Samuel Wilson (1766–1854) of Troy, N.Y. Wilson, whose nickname was Uncle Sam, was an inspector of army supplies, and the "U.S." stamped on supplies was reported to have been referred to as "Uncle Sam" by workers. Regardless of origin, the term found wide application and became permanent.
personifies people or government of the United States. [Am. Hist.: Hart, 870–871]
personification of U.S. government. [Am. Folklore: Misc.]
a personification of the government of the United States