So, interesting thing, how when I visit this site for the first time (in Firefox) is the search box showing a drop down with a bunch of my previous searches?

So, interesting thing, how when I visit this site for the first time (in Firefox) is the search box showing a drop down with a bunch of my previous searches? I can't tell where they are from but it is all stuff I have searched for in the past. I thought it might be the browser populating a list but that should be based on same domain. So where is it pulling this from? Some of the searche terms are months, perhaps more than a year old.