It was 10 years ago today that the word "Web log" was coined by a guy named Jorn Barger who maintained a website with his opinion and comments on a variety of subjects.
Two years later, online journal author Peter Merholz took the word "weblog"
and split it into "We blog."
Not long after, blog became the favored word for a weblog, and it remains so today.
You can read the whole story on NPR. They even provide a pretty interesting timeline of how the internet, the world wide web and blogs evolved.