Google Search History is the former name of the Google Web History service. This service is offered to users with a Google account. When enabled, the service stores all searches in a database. These stored search results can be viewed, and they are used to refine future Google searches based on the patterns exhibited in past searches.

Disabling Google Web History

If you are concerned with your privacy or simply do not like the altered search results Google provides based on your search history, disabling the service is your best course of action. From the Google main page, sign in to your account if you haven't already. Once signed in, click the "Settings" link in the upper right corner and choose "Google account settings" from the drop-down menu. On the "My Account" page, go to "My products" and look for the "Web History" link. (There's a little maginifying glass icon next to it.) Click that link. On the "Web History" page, click "Pause." This will stop Google Web History from collecting any more data on your searches. Then click "Remove Items." This will put you in "edit mode." You can select all items and delete them. If you ever want to resume using Google Web History, simply repeat this process and click "Resume" where earlier you clicked "Pause."

Deleting Google Web History

If you want to be rid of the Google Web History service altogether, you can delete it on your "My Account" page. Follow the procedure described above to get to your account page. Click the "Edit" link next to "My products." On the next page, click "Delete Web History permanently."

Source:

Using Web History: Deleting | Google Help