rattler (n.)

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.

venomous serpent of the Americas noted for the rattle at the end of its tail, 1620s, from rattle + snake (n.).

RATTLE-SNAKE COCKTAIL.*

*So called because it will either cure Rattlesnake bite, or kill Rattlesnakes, or make you see them.

[Harry Craddock, "The Savoy Cocktail Book," 1930]