"Mackerel snapper" was once a sectarian slur for Roman Catholics, originating in the United States in the 1850s. It referred to the Catholic discipline of Friday abstinence from red meat and poultry, for which fish was substituted. That practice distinguished Catholics from other Christians, especially in North America, where Protestant churches prevailed and Catholics tended to be poor immigrants from Italy, Poland, and Ireland.
Catholics who have celebrated their 14th birthday are still called to abstain from meat on Ash Wednesday, Good Friday, and every Friday of Lent. In addition to abstaining from meat, Catholics who have celebrated their 18th birthday, until they celebrate their 59th birthday, are to fast (may only eat one full meal with exception for health reasons) on Ash Wednesday and Good Friday. Fridays throughout the year are days of penance, but forms of penance may be substituted at the discretion of national bishops' conferences, and may include works of charity instead of abstaining from meat.
The term has been considered jocular since the mid-20th century and has fallen into disuse.
One example of the term's use comes from a letter to University of Notre Dame's president Father Matthew Walsh, from an anonymous Klansman who was upset with the actions of Notre Dame students in breaking up a Klan rally in South Bend.
The term was also used by a character in the motion picture Heaven Knows, Mr. Allison, set in the South Pacific during 1944 (the screenplay compares the rituals and commitment of the Roman Catholic Church and the United States Marine Corps). In the film, the non-Catholic U.S. Marine Corporal Allison (Robert Mitchum) refers to some fellow Marines as "mackerel snappers" while talking with a Catholic nun, then catches himself and quickly explains away his faux pas by stating that they were the "best Marines".
The term is also included in the novel The Sun Also Rises by Ernest Hemingway: "They thought we were snappers, all right," the man said. "It certainly shows you the power of the Catholic Church. It's a pity you boys aint Catholics. You could get a meal, then, all right."
- The New Partridge Dictionary of Slang and Unconventional English p. 1250 (2005 Taylor & Francis)
- "Penitential Practices for Today's Catholics". United States Conference of Catholic Bishops. Retrieved 2011-07-03.
- Colin B. Donovan, STL. "The Holy Season of Lent". EWTN. Retrieved 2009-02-25.
- "Notre Dame – 100 Years: Chapter XXVI". Retrieved 2009-09-12.
- Tucker, Todd (2004-08). Notre Dame vs. the Klan. Loyola Press. p. 177. ISBN 978-0-8294-1771-5. Check date values in: