Googlebot tries to submit searches if your website has a search form on it. Below, you can see a screenshot of a website log. It shows that googlebot submitted a search to find pages.
The following page from the Google webmaster blog explains how Googlebot proceeds when it finds a <FORM> tag. The goal was to find pages that were invisible to the public. Now, you may understand why there are options in WordPress SEO plugins to add a “
If you want to disable this