Pulling together interesting search trends and patterns requires both computing power and human power too. Search statistics are automatically generated based on the billions of searches conducted on Google. With some help from humans, and a pigeon or two when they have time, these statistics and trends make their way from the depths of Google’s hard drives to become the Google Zeitgeist findings.

Zeitgeist Explained
zeit·geist | Pronunciation: ‘tsIt-“gIst, ‘zIt | Function: noun | Etymology: German, from Zeit (time) + Geist (spirit) | Date: 1884 | Meaning: the general intellectual, moral, and cultural climate of an era.
 
http://www.google.com/intl/en/press/zeitgeist.html