According to Ryan Whitwam for Geek.com: "Frightgeist is a play on the Google Zeitgeist roundup, which is an analysis of search trends the company does every year. Frightgeist operates in a similar way in that it uses search frequency to extrapolate trends, but it’s only for Halloween costumes. Because the stats are based on search terms, some of them are a bit odd. You can probably figure out what people were going for, though.
The main Frightgeist interface is an interactive map of the US with floating bubbles over medium and large metropolitan areas — basically anywhere Google has enough search data to rank potential costumes. Hover over one and it’ll tell you which costume is the most popular search, then you can click to see more stats. Clicking on individual costumes in the results gives you data about how it has trended over the years and how it compares to other costumes in its category."
To learn more read "Google’s Frightgeist map will give you the most unique Halloween costume" from Geek.com or visit Google’s Frightgeist map.