In the past year you might had searched a lot of people, group and stuff on Facebook, but most of us can not delete our Facebook history, So here is the step by step way to do that, I hope that it will be helpful to you.
Remove Facebook Search History
First of all go to your own facebook profile through clicking on you small written name at top bar. and then click the "Activity Log Button" as shown in below images
After clicking the above mentioned activitly log button, you will find a screen similar to below image and then click on the more as shown below.
Then you will find the more options, however you will be needed to find the Search option, shown as below
And then you will finally find the option called Clear Searches
I believe that you have learned to Remove Facebook Search History.