a way of referring to the United States of America or the US government (sometimes shown as a tall man with a white beard and a tall hat) He owed $20 000 in tax to Uncle Sam. More Like This Expressions with people’s names Aunt Sally, Hobson’s choice, Hooray Henry, Houdini, Jack the Lad, Jack Robinson, Jane Doe, Joe Bloggs, Joe Public, Joe Sixpack, John Bull, John Doe, John Hancock, Johnny Reb, PC Plod, Uncle SamSee worksheet. Culture Uncle Sam became an official symbol in 1961. Uncle Sam has a white beard and wears red, white and blue clothes, with stars on his tall hat. He was probably named after 'Uncle' Sam Wilson (1766-1854), who examined army supplies for the US government during the War of 1812. During both world wars, a picture of Uncle Sam appeared on posters (= large printed notices) telling young men that they should join the armed forces. Word Origin early 19th cent.: said (from the time of the first recorded instances) to have arisen as an expansion of the letters US.