The so popular word SPAM comes from a canned meat that was … mainly in the United States. The word SPAM comes from geeting toghether the words SPiced hAM ( low quality ham).
Why is the word SPAM used for unsolicited e-mail? Well, everything started with a Monty Python video, in which the word SPAM was excevively used.
Here you can watch the video with spanish subtitles:
The word SPAM appeared on the early 1980s when some users who frequented BBSs and MUDs, who would repeat "SPAM" a huge number of times to scroll other users' text off the screen. This act, came to be known as spamming. I t later came to be used on Usenet to mean the repeated posting of the same message.
Since then the word SPAM is applied to unsolicited sent e-mails. Although e-mail is not the only way of spam, forums, web directories and instant messaging services are also affected by SPAM.
This was a brief explanation in what SPAM means. Hopefully, it was useful for you.