Is Google auto-complete based on past queries?
Yes. Google auto-complete uses an algorithm that predicts and displays search queries based on queries that have been submitted by other Google users in the past. In addition to this, if you are signed into your Google account and you also have Web History enabled, then you will see queries that show up based on the related searches (if any( that you have done in the past. All of the queries that show up in the auto-complete have been submitted by Google users in the past.