Jap

Jap is an English abbreviation of the word "Japanese". Today, it is generally regarded as an ethnic slur among Japanese minority populations in other countries, although English-speaking countries differ in the degree to which they consider the term offensive. 
In the United States, Japanese Americans have come to find the term very offensive, even when used as an abbreviation. Prior to the Attack on Pearl Harbor, Jap was not considered primarily offensive. However, following the bombing of Pearl Harbor and the Japanese declaration of war on the US, the term became derogatory, as anti-Japanese sentiment increased. During the war, signs using the epithet, with messages such as "No Japs Allowed", were hung in some businesses, with service denied to customers of Japanese descent. 
History and etymology.
According to the "Oxford English Dictionary", "Jap" as an abbreviation for "Japanese" was in colloquial use in London around 1880. An example of benign usage was the previous naming of Boondocks Road in Jefferson County, Texas, originally named "Jap Road" when it was built in 1905 to honor a popular local rice farmer from Japan.
Later popularized during World War II to describe those of Japanese descent, "Jap" was then commonly used in newspaper headlines to refer to the Japanese and Imperial Japan. "Jap" became a derogatory term during the war, more so than "Nip". Veteran and author Paul Fussell explains the usefulness of the word during the war for creating effective propaganda by saying that "Japs" "was a brisk monosyllable handy for slogans like 'Rap the Jap' or 'Let's Blast the Jap Clean Off the Map'". Some in the United States Marine Corps tried to combine the word "Japs" with "apes" to create a new description, "Japes", for the Japanese; this neologism never became popular. In post World War II America, schoolchildren often referred to an unannounced test as a "Jap quiz" in reference to the surprise attack on Pearl Harbor. The term has fallen out of favor and is largely replaced by "pop quiz".
In the United States the term is now considered derogatory; the "Merriam-Webster Online Dictionary" notes it is "disparaging". A snack food company in Chicago named Japps Foods (for the company founder) changed their name and eponymous potato chip brand to Jays Foods shortly after Pearl Harbor to avoid any negative associations with the name.
Spiro Agnew was criticized in the media in 1968 for an offhand remark referring to reporter Gene Oishi as a "fat Jap".
In Texas, under pressure from civil rights groups, Jefferson County commissioners in 2004 decided to drop the name "Jap Road" from a road near the city of Beaumont. Also in adjacent Orange County, "Jap Lane" has also been targeted by civil rights groups. The road was originally named for the contributions of Kichimatsu Kishi and the farming colony he founded. In Arizona, the state department of transportation renamed "Jap Road" near Topock, Arizona to "Bonzai Slough Road" to note the presence of Japanese agricultural workers and family-owned farms along the Colorado River there in the early 20th century. In November 2018, in Kansas, automatically generated license plates which included three digits and "JAP" were recalled after a man of Japanese ancestry saw a plate with that pattern and complained to the state.
Reaction in Japan.
Koto Matsudaira, Japan's Permanent Representatives to the United Nations, was asked about the offensiveness of the term on a television program in June 1957, and reportedly replied, "Oh, I don't care. It's English word. It's maybe American slang. I don't know. If you care, you are free to use it." Matsudaira later received a letter from the Japanese American Citizens League (JACL), and apologized for his earlier remarks upon being interviewed by reporters from Honolulu and San Francisco. He then pledged cooperation with the JACL to help eliminate the term "Jap" from daily use.
In 2003, the Japanese deputy ambassador to the United Nations, Yoshiyuki Motomura, protested the North Korean ambassador's use of the term in retaliation for a Japanese diplomat's use of the term "North Korea" instead of the official name, "Democratic People's Republic of Korea".
In 2011, after the term's offhand use in a March 26 article appearing in "The Spectator" ("white-coated Jap bloke"), the Minister of the Japanese Embassy in London protested that "most Japanese people find the word 'Japs' offensive, irrespective of the circumstances in which it is used".
Across the world.
Jap-Fest is an annual Japanese car show in Ireland. In 1970, the Japanese fashion designer Kenzo Takada opened the "Jungle Jap" boutique in Paris.
In Singapore and Hong Kong, the term is used freely as a contraction of the adjective "Japanese" rather than as a derogatory term. The Australian news service Asia Pulse has also used the term in 2008.
The word "Jap" is used in Dutch as well, where it is also considered an ethnic slur. It frequently appears in the compound "Jappenkampen" 'Jap camps', referring to Japanese internment camps for Dutch citizens in the Japanese-occupied Dutch Indies.
In Brazil, the term "japa" is sometimes used in place of the standard "japonês" as both a noun and an adjective. Although not considered offensive in the vein of the English "Jap", its use assumes a familiarity with the interlocutor that may be inappropriate in formal contexts. Moreover, while common, the use of "japa" in reference to any person of East Asian appearance, regardless of their specific ancestry, carries a pejorative connotation.