When the end of the world did not take place ...
Lookups peaked on May 21, 2011.
A religious radio host predicted that the Christian day of judgment - when, according to some, believers are physically lifted into heaven in an event known as "the Rapture" - would occur on May 21, 2011.
The end of the world did not take place, but many people went to the dictionary to look up rapture.
Rapture can mean "a feeling of great happiness or pleasure," but in this religious context it means "the final assumption of Christians into heaven." In English, the word originally meant "abduction."