Chevaliers are reformed humans turned into bodyguard like beings that travel with their queens. They stay in their original human forms until if necessary, their queens are in danger, like Hagi is with Saya.
Definitions of chevalier on the Web:
French actor and cabaret singer (1888-1972) cavalier: a gallant or courtly gentleman wordnet.princeton.edu/perl/webwn
Also is a knight in french in other words...
Jules Chevalier was born on March 15, 1824 and died on October 21, 1907. Jules Chevalier would have been 83 years old at the time of death or 188 years old today.