Spam was introduced by Hormel on July 5, 1937. The Oxford Encyclopedia of Food and Drink in America states that the product was intended to increase the sale of pork shoulder which was not a very popular cut. Ken Daigneau, brother of a company executive, won a $100 prize that year in a competition to name the new item. Hormel claims that the meaning of the name "is known by only a small circle of former Hormel Foods executives", but popular beliefs are that the name is an abbreviation of "spiced ham". The difficulty of delivering fresh meat to the front during World War II saw Spam become a ubiquitous part of the U.S. soldier's diet. It became variously referred to as "ham that didn't pass its physical", "meatloaf without basic training", and "Special Army Meat". Over 68,000 tonnes (150 million pounds) of Spam were purchased by the military before the war's end.

During World War II and the occupations which followed, Spam was introduced into Guam, Hawaii, Okinawa, the Philippines, and other islands in the Pacific. Immediately absorbed into native diets, it has become a unique part of the history and effects of U.S. influence in the Pacific islands.