Do you also see those search words which you have searched earlier as soon as you start typing on the text box in Firefox. That could be very annoying sometimes letting others know what you are searching for.
Follow these steps to hide your internet search history
-> From the Tools menu bar in Firefox at the top select Options. A new Options Window will open up.
-> From the Privacy Tab uncheck the option Remember what I enter in forms and the search bar.
-> Press OK Button and you are done! So from now onwards you won’t be seeing those annoying popups when you enter information on forms and search bar in Firefox
But if you are still concerned about your search information history you can also delete it permanently without leaving any trace.
good post