rattlesnake 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.

Middle English snake, "a long, limbless reptile," from Old English snaca, from Proto-Germanic *snakon (source also of Old Norse snakr "snake," Swedish snok, German Schnake "ring snake"), from PIE root *sneg- "to crawl, creeping thing" (source also of Old Irish snaighim "to creep," Lithuanian snakė "snail," Old High German snahhan "to creep"). In Modern English, gradually replacing serpent in popular use.

Traditionally applied to the British serpent, as distinguished from the venomous adder. Applied from 17c. to various snake-like devices and appliances. Snakes! as an exclamation is from 1839.

The meaning "treacherous person" is attested by 1580s (it was used of Satan in early 15c., and serpent and adder are older in this sense) Compare Old Church Slavonic gadu "reptile," gadinu "foul, hateful." The snake's reputation was not helped by the Genesis story, but the notion is older. The phrase snake in the grass "underhand, plotting, deceitful person" translates Virgil's Latet anguis in herba [Ecl. III:93].

Snake eyes in crap-shooting, "a throw of two ones" (the lowest possible roll), is from 1919, hence the association with bad luck. This might have influenced snake-bitten, snake-bit "unlucky," attested in sports slang by 1957, which also might be from a literal sense (attested by 1807), perhaps suggesting one doomed by a venomous bite.

The board game of Snakes and Ladders is attested from 1907. Snake charmer is from 1813. Snake pit is from 1883, as a supposed primitive test of truth or courage; the figurative sense is from 1941. Snake dance is by 1772 in reference to a Hopi ceremony; by 1911 as a party dance.

mid-15c., "one who talks overmuch, without reflection or consideration;" agent noun from rattle (v.). From c. 1300 as a surname. As short for rattlesnake, 1827.