Where does the name Blog come from?

Blog is short for the word 'Web-log' which is like a online journal where you can post what you want and as frequent as you want and can then be posted on a website for other people to read. 

When was the first blog created and by whom?

The first blog was made in 1997 by Ian Ring who had single handily created the blog but he had named it e-journal at the time.

How much personal information should you have on your Blog? 

It is completely personal preference how much personal information should be on blogs but there should be a limit because you don't know who could visit your blog.

What is the general term for all the Blogs that have been created?

The Blogosphere is the term that is used for all the blogs that have been created.