This word was created from the world rad. It became 'red' because the creators, Emz and Renn, were tired of people stealing their red words, and turning them into something they weren't. It was named, therefore, after Emz and Renn, because it incorporates both of their names into one word, plus adding the ending of the word 'rad' into it, as well.
Red is another way of expressing how cool something is, although it is a stronger world than 'cool'
An example of using this word, is shown below...
'Your shoes are really red'
'I know, aren't they the reddest?'
It basically translates to 'it's really cool, but not as cool as Emz and Renn'