Where does the term "element" come from?

["Costello, Roger L." <costello@mitre.org>]

Hi Folks,

This is a book element:

   <book>...</book>

Why "element"?

Who decided to call it element? 

When was the term first used?

There is the Periodic Table of elements. Is that where the term comes from?

In hindsight, is there a better term?

/Roger