So define "Blog" for me

So my friends have decided blogging is the new shit, so here i am following the masses.

But this raises the question: What the hell does blog/blogging mean?

To me "blog" sounds like a bog containing lots of random floating logs. And if so, why did this become the newest fad? Did something momentous occur at the infamous blog? like perhaps this is where Walt Whitman ran away to write his "Leaves of Grass." The first known "blog" to mankind?

What are your thoughts?