NFL is an American football abbreviation. "NFL" stands for "National Football League". National because the league is played across the nation; Football because the game played is referred to as "football" (It is known as "football" in America. Many countries refer to it a "soccer".); League because this national game is played with multiple teams in many places at different times, etc. (unapproved definition of "league").
You can find it at the National Football League website @ NFL.com.
National Indoor Football League ended in 2008.
National Indoor Football League was created in 2001.
Newman National Football League was created in 1972.
National Football League was created on 1920-08-20.
Fortescue National Football League was created in 1956.
The National Football League was founded in 1920 under the name American Professional Football Association. The name was changed to National Football League in 1922.
National Football League Players Association was created in 1956.
Korean National Youth Football League was created in 2009.
National Football League Kickoff game was created in 2002.
South Australian National Football League was created in 1877.