batten down the hatches - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Prepare for trouble, as in Here comes the boss—batten down the hatches. This term originated in the navy, where it signified preparing for a storm by fastening down canvas over doorways and hatches (openings) with strips of wood called battens. [Late 1800s]