How it works
If you click the 'normalize' link on the cities tab, it explains how they do the ranking.
I think they pick the top ten cities with the most searches for the term entered, then they rank those in order of percentage of total searches for each city.
So the city with the highest overall number of searches for a term might well be at number 7 or whatever. And even the city with the highest overall ratio of searches for a given term might not even be in the ranking at all (if it didn't have a top ten placing for searches on that term)
For instance, for eskimos at the North Pole, there's probably a high ratio of searches for the term 'penguin' to total searches. Up there, 99% of searches are probably for one of 'penguin', 'snow', or 'wankers'.
Type it into Google trends though, and just a load of Ozzie cities come up - even though only a maximum of half all searches from Oz could realistically contain that word. There's another surprise with Thames Ditton, which tops the rankings, but presumably because of all the concerned mums checking the nutritional value of their kids' snacks.