Amazon searches

I love Amazon.com, but I can't understand why it recommends the following books to me when I search for "Rugby for Dummies"

• European History for Dummies (ok, this one makes a little sense)
• The Romans for Dummies (did the Romans invent rugby?)
  
• Personal Development for Dummies (I guess learning the rules of rugby could be seen as "personal development," but it's a bit of a stretch)
• DJing for Dummies (huh?)
• Managing PCOS for Dummies (I think, and I could be wrong, that PCOS is a computer programming language. Maybe they think after I learn about rugby that I'll develop software to help me play.)
  

And my personal favorite...

• Pregnancy for Dummies (I have no idea what rugby and pregnancy have in common. Maybe if I read both of these books I'll find out)