The term 'Oklahoman, informally' can be summarized as 'SOONER', which is a 6-letter word. The term 'SOONER' is used to refer to a native or resident of the U.S. state of Oklahoma. The term is derived from the early settlers of the Oklahoma Territory who entered the land before the official opening date set by the federal government. This group of settlers were known as 'Sooners' and the term has since become a popular nickname for all Oklahomans.