It’s about time. We are now on Instagram!
late 14c., "to cut down or off," from under + cut (v.). In the commercial sense of "to sell at lower prices" (or work at lower wages) it is first attested 1884. Figurative sense of "render unstable, undermine" is recorded from 1955, from earlier literal meaning "cut so as to leave the upper portion larger than the lower" (1874).