In response to Aunty Spam’s Hormel Ready To Take Back The Spam, Gnomie Richard Heater writes:

Early in ‘42 I experienced the dubious pleasure of eating Spam in an army mess hall. “Spam” is a contraction of spiced-ham originated by Hormel Packing Co. In the army, it is creamed beef on toast and some of the beef may have been supplied by Hormel, but not all. The GIs had a somewhat less appetizing expression: They called it S.O.S., an acronym for S*** On a Shingle. There was a rumor that the Japanese army, not to be outdone, had devised an Asiatic equivalent consisting of creamed raw fish on toast, or, S.O.S. for Sushi On a Shingle (since beef was too scarce and expensive). Today, we have computer SPAM, an acronym for “Some Perfectly Aggravating Messages.”