How does 'related search' on twitter works?

[Anggy]

So I searched someone's account on my twitter for iPhone, when the results comes out it shows tweets mentioning him/her. On the top of the search there is a "related search" bar and it shows someone else's twitter account name (i.e searching for michaelx, it shows, related: johndoe). As far as I know, they are not related, not following each other, not know each other, and not a celebrity or some sort. Why does this happen? And how do they become related?

[Josh]

It does a related search