Originally just a canned sandwich filler product, now this term is also used to refer to the practice of blindly posting commercial messages or advertisements to a large number of unrelated and uninterested newsgroups.
http://webweevers.com/glossary3.htm
Spam is a popular Monty Python sketch, first broadcast in 1970. In the sketch, two customers are trying to order a breakfast without SPAM from a menu which includes the processed meat product in every entree. The term spam (in electronic communication) is derived from this sketch.
http://en.wikipedia.org/wiki/Spam_(Monty_Python)
