The SPAM you may not know of
(Especially, if you are an Indian, and a vegetarian)
SPAM luncheon meat is a canned precooked meat product made by the Hormel Foods Corporation. The product has become part of many jokes and urban legends about mystery meat, which has made it part of pop culture and folklore. Introduced on July 5, 1937, the name "Spam" was chosen in the 1930s when the product, whose original name was far less memorable (Hormel Spiced Ham), began to lose market share. The name was chosen from multiple entries in a naming contest. A Hormel official once stated that the original meaning of the name Spam was "Shoulder of Pork And haM".
Spam was one of the few meat products included in the British food rationing that began in World War II (and continued for a number of years after the war), and the British grew heartily tired of it.The Monty Python comedy troupe used this as the context for their "Spam" sketch, in which the menu at a greasy spoon cafe consists entirely of dishes containing one or more portions of Spam.
Now, the spam you do know of
(Presuming you hold an email account and check it frequently too. Notice the use of small letters, unlike the capital letters in the brand name, as prescribed by the law.)
The repetitious nature of the Monty Python sketch, in which the customer becomes more and more exasperated by the appearances of "Spam" in every menu item, gave rise to the term Spam as the common term for unsolicited bulk electronic messages. Earlier, the term was used as a verb to describe widespread dissemination of derogatory (and often untrue) postings and messages about a person ("She was getting spammed all over the Internet.").
Hormel does not object to the term, but insists that it be spelled in lower case so as to distinguish it from its capitalized SPAM trademark. Hormel objects to Spam's "product identity" (for example, images of Spam cans) being used in relation to spamming, and has filed lawsuits against companies which have attempted to trademark words containing "Spam".
In 1998, the New Oxford Dictionary of English, which had previously only defined "Spam" in relation to the trademarked food product, added a second definition to its entry: "Irrelevant or inappropriate messages sent on the Internet to a large number of newsgroups or users."
(Edited from a wikipedia article)