Jap (n.)

colloquial abbreviation of Japanese, 1877, perhaps encouraged or inspired by the common abbreviation Jap.; it was not originally pejorative, but it became intensely so during World War II. It was protested by Japanese before the war, but did not begin to be taboo in the U.S. before 1960s. As an adjective from 1878. For some years after World War II in American English the word also functioned as a verb, "to execute a sneak attack upon," a reference to Pearl Harbor.