|Look up Wop in Wiktionary, the free dictionary.|
According to Merriam-Webster, its first known use was in the United States in 1908. The dictionary is unambiguous that it originates from a Southern Italian dialect term guappo, meaning thug, pimp, or swaggerer, derived from the Spanish term guapo, meaning handsome, via dialectical French, meaning ruffian or pimp. It also has roots in the Latin vappa, meaning wine gone flat.
In Neapolitan language and other Southern Italian languages, guappo is pronounced as wah-po. As Southern Italian dialects often feature unaspirated stops or "swallow" the final vowels in a word, guappo would often sound closer to wahpp to American or Anglo ears. Guappo historically refers to a type of flashy, boisterous, swaggering, dandy-like criminal in the Naples area, portrayed as free-spirited yet often violent and taking part in criminal enterprises such as extortion, usury, and procuring. The word eventually became associated with members of the Camorra and has often been used in the Naples area as a friendly or humorous term of address among men. The word likely transformed into the slur "wop" following the arrival of Southern Italian immigrants into the United States. Southern Italian immigrant males would often refer to one another as "guappo" in a jocular or playful manner; as these Southern Italian immigrants often worked as manual laborers in the United States, their native-born American employers and fellow laborers took notice of the Italians' playful term of address and eventually began deploying it as a derogatory term for all Italians.  The term "guappo" was especially used by older Southern Italian immigrant males to refer to the younger Southern Italian male immigrants arriving in America. 
A false etymology or backronym sometimes promulgated is that "wop" is an acronym that comes from "without passport" or "without papers", implying that Italian immigrants entered the U.S. as undocumented or illegal immigrants. The term has nothing to do with immigration documents, as these were not required by U.S. immigration officers until 1918, after the slur had already came into use in the United States. Further, turning acronyms into words did not become common practice until after World War II, with the practice accelerating with the growth of the United States space program and the Cold War. The term has also been said to stand for "working on pavement," as many Italian immigrants and Italian-American men worked in and have been stereotyped as working in construction, manual labor, and masonry.
- Embury, Stuart P. (2006). "Chapter One: The Early Years". The Art and Life of Luigi Lucioni. Embury Publishing Company. pp. 1-4.
- Wop. Merriam-webster.com. Retrieved on 2015-10-11.
- Wop. Dictionary.reference.com. Retrieved on 2015-10-11.
- Delgado, Richard; Stefancic, Jean (2004). Understanding Words That Wound. Westview Press. p. 57.
- Mencken, H.L. (2012). American Language Supplement 1. Knopf Doubleday Publishing Group. pp. 604–605.
- (Italian) Quando il guappo non era camorrista, Il Denaro Nr. 159, August 26, 2006
- Csóti (2002). Contentious Issues: Discussion Stories for Young People. Jessica Kingsley Publishers.
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- Will, George (September 23, 2015). "Yogi Berra, an American Story". National Review. Washington Post. Retrieved 1 October 2015.
- Rappoport, Leon (2005). Punchlines: The Case for Racial, Ethnic, and Gender Humor. Greenwood Publishing Group.
- Milian, Claudia (2013). Latining America: Black-Brown Passages and the Coloring of Latino/a Studies. University of Georgia Press.