blog (n.) Look up blog at Dictionary.com
1998, short for weblog (which is attested from 1994, though not in the sense "online journal"), from (World Wide) Web + log. Joe Bloggs (c.1969) was British slang for "any hypothetical person" (compare U.S. equivalent Joe Blow); earlier blog meant "a servant boy" in one of the college houses (c.1860, see Partridge, who describes this use as a "perversion of bloke"), and, as a verb, "to defeat" in schoolboy slang. The Blogger online publishing service was launched in 1999.