1540s (trans.), 1560s (intrans.), variant of Middle English huisht (late 14c.), probably of imitative origin, with terminal -t lost probably by being mistaken for a past tense suffix. The sounds chosen presumably for "being sibilations requiring the least muscular effort and admitting of the faintest utterance" [Century Dictionary]. Related: Hushed; hushing.
Figurative use from 1630s. 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 "bribe paid to ensure silence" 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.
lullaby n.
"soothing song sung to infants," 1580s, noun use of the words lulley by (1560s), from Middle English lollai or lullay, a common burden in nursery songs, from lullen (see lull (v.)). Second element perhaps from by in good-bye or simply a meaningless extension.