Trending keywords move with the news cycles, reflecting the latest and most important events. With the shutdown of Napster in 2000, these leading search engines saw a spike in searches for the phrases: file sharing and peer-to-peer file sharing.
After that, the search engine rankings for those terms changed dramatically because so many people were looking for them. Because of this effect, short-term fresh keywords have a very high commercial value, and we should always try to rank our content for them.