Is it ensure, insure, or assure?
late 14c., weapon of war, from battle (n.) + axe (n.); meaning "formidable woman" is U.S. slang, first recorded 1896.
An ill-tempered woman, esp a mean old woman; virago (1890s+)
a mallet or heavy war-club. Applied metaphorically (Jer. 51:20) to Cyrus, God's instrument in destroying Babylon.