Each time you search for something on Facebook, search terms are stored in the Activity Log. This is how to see (and delete if you want).
The activity log is visible only to you, but if you want to delete one of your old searches for any reason, or even if you just want to see (for something you forgot) – it’s very easy to find!
Click the gear icon in the upper right corner of Facebook and access the activity log. From there, click the “More” button in the left sidebar to display the “Search”. Click to display search history. If you want to delete it, there is a button in the upper right corner to do just that.
We have not been able to find a setting that completely transforms this story, unfortunately, but again, the messages are visible only to you, so it should not be a big problem.