in irons vs in prison

in irons

prep
  • The state of screw-powered ships which become stalled between crests of waves or swells during a typhoon, for instance, and the ship's rudder does not respond to the commands from the helm, leaving the ship at the mercy of the sea and in danger of capsizing. 

  • The "trapped" condition a sailing ship finds itself in when the bow of the ship is headed into the wind and the ship has stalled and is unable to maneuver. 

in prison

prep
  • imprisoned; in a prison as a convict 

How often have the words in irons and in prison occurred in a corpus of books? (source: Google Ngram Viewer )