The word “Spam” comes from the name of canned meat
In 1937, the company Hormel Foods released a new type of canned meat called “Spam”, which turned out to be so successful that the American army bought them in huge excess. Canned food was in demand after the war, and gave rise to the fashion for canned food in everyday life. They literally filled all the shops, which was ridiculed in the 1970s in the Monty Python show.
The word “spam” became associated with something massive and annoying, so when unwanted mailings appeared in the 90s with the birth of the Internet, it had to be used to denote a new phenomenon.