c. 1300 (intransitive), "To make a quick sharp noise with frequent repetitions and collisions of bodies not very sonorous: when bodies are sonorous, it is called jingling" [Johnson]. Perhaps in Old English but not recorded; if not, from Middle Dutch ratelen, which is probably of imitative origin (compare German rasseln "to rattle," Greek kradao "I rattle").
The sense of "utter smartly and rapidly, speak with noisy and rapid utterance" is attested by late 14c. The meaning "to go along loosely and noisily" is from 1550s. The transitive sense is from late 14c. The colloquial American English figurative meaning of "fluster, shake up, unsettle" is attested by 1869, on the notion of "startle or stir up by noisy means." Related: Rattled; rattling.
c. 1500, "rapid succession of short, sharp sounds," from rattle (v.). As a child's toy or other instrument contrived to make a rattling sound, from 1510s. As a sound made in the throat (especially of one near death) from 1752.
The watchman's rattle, formerly used for giving an alarm, and the child's toy resembling it, consist of a vibrating tongue slipping over the teeth of a rotating ratchet-wheel, and producing much noise when rapidly twirled by the handle. [Century Dictionary]