Every wonder where and how the term "Search Engine Optimization" came about? Danny Sullivan answered, to the best of his knowledge, how and when this term was popularized at the Search Engine Watch Forums. Please read the post for the complete detail, I will just pull out a few dates but its best to read the post in its context.
"May 1997: First reference I [Danny Sullivan] find within SEW to the exact phrase "search engine optimization," but only within a meta tag."
"July 1997: First reference I can find in newsgroups to the phrase "search engine optimization," from a company pitching these services."
Please read the post in its entirety.