Emily Dickinson Lexicon

ROCK, v.t. [Dan. rokker, to move, stir, wag, rack, advance; G. rücken; Old Fr. rocquer or roquer; Sw. ragla, to reel; W. rhocian, to rock; rhoc, a shooting or moving different ways; Ar. رَجَّ ragga, to shake, to tremble, to agitate. This latter verb in Ch. and Syr. signifies to desire, to long for, that is, to reach or stretch, Gr. ορεγω; and it may be a different word.]

1. To move backward and forward, as a body resting on a foundation; as, to rock a cradle; to rock a chair; to rock a mountain. It differs from shake, as denoting a slower and more uniform motion, or larger movements. It differs from swing, which expresses a vibratory motion of something suspended. A rising earthquake rock'd the ground. – Dryden.
2. To move backward and forward in a cradle, chair, &c.; as, to rock a child to sleep. – Dryden.
3. To lull to quiet. Sleep rock thy brain. [Unusual.] – Shak.