What you are looking for is a Random Text Selector.
Google brought this up when I searched for it:
Select Random LI element[
^]
If it were me, I would go through the code and see how it works, then tinker around with it. I would then see if I could
abuse the ability of jquery/javascript to parse the DOM and place the random content in non-visible elements (probably via CSS and a UL-LI).
Once my skills developed, I would put the data into external files (content1, content2) and use that same random generator to select one of them external files to get the random content.