undermine (v.) Look up undermine at Dictionary.com
c.1300, undermyne, "render unstable by digging at the foundation," from under + mine (v.). The figurative sense "injure by invisible, secret, or dishonorable means" is attested from early 15c. Similar formation in Dutch ondermijnen, Danish underminere, German unterminiren. The Old English verb was underdelfan. Related: Undermined; undermining.