snitch (n.)youdaoicibaDictYouDict[snitch 词源字典]
"informer," 1785, probably from underworld slang meaning "the nose" (1700), which apparently developed from an earlier meaning "fillip on the nose" (1670s). Snitcher in same sense is from 1827.[snitch etymology, snitch origin, 英语词源]
snitch (v.)youdaoicibaDictYouDict
1803, "to inform," from snitch (n.). Meaning "to steal, pilfer" is attested from 1904, perhaps a variant of snatch (v.). Related: Snitched; snitching.