The term SPAM (for email) came from a Monty sketch about the said meaty tin.
Check it out on WikiPudding
Only three and a half minutes long, it builds up into a semi-argument between the waitress who has a menu limited to having Spam in just about everything (among them, “Lobster Thermidor aux crevettes with a Mornay sauce, garnished with truffle pâté, brandy and a fried egg on top and Spam”), and Mrs Bun, who is the only one in the room who does not want Spam. She asks for an item with the Spam removed (despite there already being some items mentioned that do not actually include Spam), much to the amazement of her Spam-loving husband. The waitress responds to this request with great disgust. Eventually, Mrs Bun resorts to screaming, “I DON’T LIKE SPAM!!”
At several points, a group of Vikings in the restaurant (referred to as the Green Midget Café in Bromley) interrupt conversation by loudly singing “Spam, lovely Spam, wonderful Spam.” They are ordered to “shut up” by the irate waitress several times, but they resume singing more and more loudly. Then a Hungarian tourist comes to the counter, trying to order by using a wholly inaccurate Hungarian/English phrasebook (a reference to a previous sketch). He is rapidly escorted away by a police constable.
The sketch abruptly cuts to a historian in a television studio talking about the Vikings. As he goes on, he begins to uncontrollably insert the word ‘spam’ into everything he says (“…and Spam selecting a Spam particular Spam item from the Spam menu, would Spam, Spam, Spam, Spam…”), and the backdrop is lifted to reveal the restaurant set behind. The historian joins the Vikings, Mr. and Mrs. Bun are lifted by wires out of the scene and the singing continues on and on…
It premiered on 15 December 1970 as the final sketch of the 25th show of Monty Python’s Flying Circus, and the following end credits were changed so every member of the crew has either Spam or some other food item from the menu added to their names. (Spam Terry Jones, Michael Spam Palin, John Spam John Spam John Spam Cleese, Graham Spam Spam Spam Chapman, Eric Spam Egg and Chips Idle, Terry Spam Sausage Spam Egg Spam Gilliam, etc.) The sketch became immensely popular. The word Spam is uttered at least 132 times.