TGIF is an initialism for the phrase "Thank God

God

God is the English name given to a singular being in theistic and deistic religions who is either the sole deity in monotheism, or a single deity in polytheism....

 (or Goodness) It's Friday

Friday

Friday is the day between Thursday and Saturday. In countries adopting Monday-first conventions as recommended by the international standard ISO 8601, it is the fifth day of the week. It is the sixth day in countries that adopt a Sunday-first convention as in Abrahamic tradition...

", celebrating the last day of the work/school week before the weekend

Workweek and weekend

The workweek and weekend are those complementary parts of the week devoted to labour and rest respectively. The legal working week , or workweek , is the part of the seven-day week devoted to labor. In most Western countries it is Monday to Friday. The weekend comprises the two traditionally...

. Its origin dates to the 1960s. It was first popularized by the restaurant T.G.I. Friday's

T.G.I. Friday's

T.G.I. Friday's is an American restaurant chain focusing on casual dining. The company is a unit of the Carlson Companies. Its name is taken from the expression TGIF...

 which was founded in 1965. However, it became mainstream by the late 1970s, mainly due to the 1978 movie of the same name. It is also an acronym for Toes Go In First, which is the punch-line of various blonde jokes.

Popular culture

• In 2011, Katy Perry
  Katy Perry
  Katy Perry is an American singer, songwriter and actress. Born in Santa Barbara, California, and raised by Christian pastor parents, Perry grew up listening to only gospel music and sang in her local church as a child. After earning a GED during her first year of high school, she began to pursue a...
  
   released a song mentioning T.G.I.F., called "Last Friday Night (T.G.I.F.)
  Last Friday Night (T.G.I.F.)
  "Last Friday Night " is a song by American recording artist Katy Perry. The song was produced by Lukasz Gottwald and Max Martin, who also co-wrote the song with Perry and Bonnie McKee for Perry's third studio album, Teenage Dream. Perry stated that she was inspired to write the track after a night...
  
  " .
• Hip-Hop artist's Kid Cudi
  Kid Cudi
  Scott Ramon Seguro Mescudi , better known by his stage name Kid Cudi , sometimes stylized KiD CuDi, is an American rapper, singer and actor. He first gained major attention after the release of his debut mixtape A Kid Named Cudi. In 2009, his single "Day 'n' Nite" reached the top five of the...
  
   and Chip Tha Ripper released a song named "T.G.I.F. (Thank God I'm Fresh)".
• TGIF
  TGIF (ABC)
  TGIF was the name of an American family-friendly prime time television programming block on the ABC network. The name comes from the initials of the popular phrase "Thank God It's Friday"...
  
   was the name of an American family-friendly prime time programming block on the ABC network.
• In the episode "The End" in HBO's Curb Your Enthusiasm
  Curb Your Enthusiasm
  Curb Your Enthusiasm is an American comedy television series produced and broadcast by HBO, which premiered on October 15, 2000. As of 2011, it has completed 80 episodes over eight seasons. The series was created by Seinfeld co-creator Larry David, who stars as a fictionalized version of himself...
  
  , Larry sports a TGIF t-shirt, after discovering that he is apparently Gentile and not Jewish.
• For a long time on American network television (and maybe even now), there was an ad for the TGI Fridays restaurant chain that mentioned T.G.I.F.