Except for the part about the term starting in the UK in the 1880s as slang for Association Football to distinguish it from ~~rugger~~ "Rugby Football" where it later fell out of fashion but by then had made it's way to America and, due to the popularity of Gridiron Football taking the name "football," needed to be distinguished by another name, and what better to use than the previously established slang term, from Britain, "soccer."