Blog, a frequently updated website consisting of chronlogical observations (typically by a single person), is a shortening of the word weblog.
The term weblog was coined by John Barger, who first used it on the 17th December 1997 to describe the links that logged his internet wanderings on his website. Two years later, Peter Merholz coined the word blog by splitting the word weblog in "we blog" in a sidebar on his personal site Peterme.com, writing "For What It's Worth: I've decided to pronounce the word "weblog" as wee'- blog. Or "blog" for short."
However, it was Evan Williams and Meg Hourihan, the co-founders of Pyra Labs, who would popularise the term and use it in the verb form blogging, with the launch of their blogging platform Blogger. Williams, who would later found Twitter and Medium, who is credited with term blogger.
"Evan Williams came up with the name "Blogger" for our product," said Hourihan. "When we set about to write the copy for the site, we used the word "blog" for
every instance of "weblog." There was no other service at the time that used that term. I think it's fair to say that the popularity of our service led to the popularization of the term "blog" and its now ubiquitous use.
Source: After 10 years of blogs... | Peterme.com. | Email from Meg Hourihan