This idiom means to prepare for trouble, difficulty, or a challenging situation by securing resources or defenses. Originally nautical, it now applies to any scenario requiring readiness, such as bracing for a storm, crisis, or conflict, and conveys urgency and precaution.

The phrase comes from 19th-century naval terminology, where sailors would ‘batten down’ ship hatches with wooden strips (battens) to secure them against storms. An early use appears in an 1840 maritime journal: ‘Batten down the hatches before the gale.’ By the late 19th century, it was used metaphorically in American and British English, especially in journalism, to describe preparing for crises, as seen during the U.S. Civil War. Its vivid imagery ensured its lasting use.