Most of you have heard the story.
Originally, SPAM is a 1937 trademark by Jey Hornel who put together the words SPiced hAM. In 1970, episode 25 of Monty Python’s Flying Circus takes place in a restaurant. There's this SPAM crap on every item of the menu : Egg and Spam, Egg Bacon and Spam, Egg Bacon Sausage and Spam, Spam Eggs Spam Spam and Spam...
A group of customers disguised as Vikings begins singing : Spam ! Spam ! Spam ! Spam ! louder and louder. The level of the singing keeps increasing until it drowns out any other possible conversation amongst the diners. Thus the reputation of SPAM regarding junk e-mail.
Here is a replay of that famous video:
http://www.youtube.com/watch?v=XZ6N5m8FpVg