The use of the word Spam to describe unwanted email, is said to have originated in this skit from the second series of "Monty Python's Flying Circus" and "Monty Python's Previous Record."

(Spam = Spiced Pork And Ham, a sort of cheap luncheon meat)

Scene: A cafe. One table is occupied by a group of Vikings with horned helmets on. A man and his wife enter.

Man (Eric Idle): You sit here, dear.
Wife (Graham Chapman in drag): All right.
Man (to Waitress): Morning!
Waitress (Terry Jones, in drag as a bit of a rat-bag): Morning!
Man: Well, what've you got?
Waitress: Well, there's egg and bacon; egg sausage and bacon; egg and spam; egg bacon and spam; egg bacon sausage and spam; spam bacon sausage and spam; spam egg spam spam bacon and spam; spam sausage spam spam bacon spam tomato and spam;
Vikings (starting to chant): Spam spam spam spam...
Waitress: ...spam spam spam egg and spam; spam spam spam spam spam spam baked beans spam spam spam...
Vikings (singing): Spam! Lovely spam! Lovely spam!
Waitress: ...or Lobster Thermidor a Crevette with a mornay sauce served in a Provencale manner with shallots and aubergines garnished with truffle pat?, brandy and with a fried egg on top and spam.
Wife: Have you got anything without spam?
Waitress: Well, there's spam egg sausage and spam, that's not got much spam in it.
Wife: I don't want ANY spam!
Man: Why can't she have egg bacon spam and sausage?
Wife: THAT'S got spam in it!
Man: Hasn't got as much spam in it as spam egg sausage and spam, has it?
Vikings: Spam spam spam spam (crescendo through next few lines)
Wife: Could you do the egg bacon spam and sausage without the spam then?
Waitress: Urgghh!
Wife: What do you mean 'Urgghh'? I don't like spam!
Vikings: Lovely spam! Wonderful spam!
Waitress: Shut up!
Vikings: Lovely spam! Wonderful spam!
Waitress: Shut up! (Vikings stop) Bloody Vikings! You can't have egg bacon spam and sausage without the spam.
Wife (shrieks): I don't like spam!
Man: Sshh, dear, don't cause a fuss. I'll have your spam. I love it. I'm having spam spam spam spam spam spam spam baked beans spam spam spam and spam!
Vikings (singing): Spam spam spam spam. Lovely spam! Wonderful spam!
Waitress: Shut up!! Baked beans are off.
Man: Well could I have her spam instead of the baked beans then?
Waitress: You mean spam spam spam spam spam spam... (but it is too late and the Vikings drown her words)
Vikings (singing elaborately): Spam spam spam spam. Lovely spam! Wonderful spam! Spam spa-a-a-a-a-am spam spa-a-a-a-a-am spam. Lovely spam! Lovely spam! Lovely spam! Lovely spam! Lovely spam! Spam spam spam spam!