Drop a dime to meet the fishes.
In February 1998 there was  a question on the origin of the British term “grass” meaning, roughly, “to snitch.” But where did the word “snitch,” which is much older, come from? The Oxford English Dictionary says it’s of unknown origin. Any thoughts on the word’s origin or on how it came to mean “grass”? — Jackie.

The use of “grass” as British slang for a police informer dates back to the 1930s, and is apparently a short form of the slang term “grasshopper,” meaning the same thing. “Grasshopper” itself is rhyming slang (”a secret language” in which words rhyme with a hidden meaning) for either “copper” (i.e., a police officer) or “shopper,” one who “shops” (sells) information to the police.

“Snitch” meaning “informer” is indeed an older word, dating back to the late 18th century. But the original meaning of “snitch” when it appeared a hundred years earlier was “a fillip on the nose,” a “fillip” being what we would today call a “flick” with one’s finger or a light, sudden slap of the hand. The actual origin of “snitch” is, as the OED says, unknown, but I would suspect an “echoic” origin, i.e., the word was intended to echo the action (and perhaps the sound) of a light, snapping tap on the schnozz. Such coinages are not uncommon. “Tap” and “slap,” for instance, are both of such “echoic” origins.

By about 1700, “snitch” had progressed from meaning “flick to the nose” to serving as slang for the nose itself (”As the … egg … broke on the ’snitch’ of the Socialist candidate,” 1902), and this was the key development in the evolution of “snitch” as slang for “informer.” The nose has long been used as a symbol of intrusion into others’ business (e.g., a busybody is described as being “nosy”), and the image of a police dog or bloodhound “sniffing out” crime or tracking criminals has been a staple of popular culture for centuries. “Nose,” in fact, has been underworld slang for a spy or informer since the late 18th century (”The first issue of forged notes, it is stated by a nose (an informer), amounted to 500,” 1830). So using “snitch,” already slang for “the nose,” as slang for “an informer” would have been a natural development.