corn-snake n.

"grain," Old English corn "single seed of a cereal plant; seeds of cereal plants generally; plants which produce corn when growing in the field," from Proto-Germanic *kurnam "small seed" (source also of Old Frisian and Old Saxon korn "grain," Middle Dutch coren, German Korn, Old Norse korn, Gothic kaurn), from PIE root *gre-no- "grain."

The sense of the Old English word was "grain with the seed still in" (as in barleycorn) rather than a particular plant. Locally understood to denote the leading crop of a district. It has been restricted to the indigenous "maize" in America (c. 1600, originally Indian corn, but the adjective was dropped), usually "wheat" in England, "oats" in Scotland and Ireland, while Korn means "rye" in parts of Germany.

Maize was introduced to China by 1550, it thrived where rice did not grow well and was a significant factor in the 18th century population boom there. Corn-starch is from 1850. Corn-silk is attested from 1852.

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.