What is cirque du freak in English?

Cirque Du Freak in English means Circus of Freaks. The reason the books are all called "Cirque Du Freak" is because in the books Darren and Mr. Crepsley go to the Cirque Du Freak to participate in the shows. The Cirque Du Freak is a freak show filled with cool, wild, and amazing creatures or "freaks".

it means something like freakshow which were banned a very long time ago due to the way they treated the freaks. basically people that wernt like other people and were different than others would goto these cirques and get put on show then people would pay and come to see the freaks for their own personal pleasure.