What word or phrase does your mother always say?
1540s, variant of Middle English huisht (late 14c.), probably of imitative origin, with terminal -t lost probably by being mistaken for a past tense suffix. Hush-hush (adj.) is 1916 reduplication. Related: Hushed; hushing. The noun is attested from 1680s. As an interjection meaning "be quiet," attested by c.1600. To hush (one's) mouth "be quiet" is attested from 1878. Hush up "suppress talk for secrecy's sake" is from 1630s. Hush-money is attested from 1709. Hush-puppy "deep-fried ball of cornmeal batter" first attested 1899; as a type of lightweight soft shoe, it is a proprietary name, registered 1961.