Ironsides /(?)/

I·ron·sides

Ironsides

n.
  1. A cuirassier or cuirassiers; also, hardy veteran soldiers; -- applied specifically to Cromwell's cavalry.

Phrases & Compounds
Old Ironsides
A nickname for the U.S.S. Constitution, a sailing ship which fought in the American Revolutionary war, and now functions as a floating museum in Boston harbor. It was given its nickname because cannonballs bounced off its hard wooden sides.