Green Grow the Lilacs is a folk song of Irish origin that was popular in the United States during the mid-19th century.
The song title is the source of a folk etymology for the word gringo that states that the Mexicans misheard U.S. troops singing "green grow" during the Mexican–American War.[1]
The song appears in the 1931 stage play of the same name by Lynn Riggs, which is the basis of the 1943 musical Oklahoma!