blue (2)youdaoicibaDictYouDict[blue 词源字典]
"lewd, indecent" recorded from 1840 (in form blueness, in an essay of Carlyle's); the sense connection is unclear, and is opposite to that in blue laws (q.v.). John Mactaggart's "Scottish Gallovidian Encyclopedia" (1824) containing odd words he had learned while growing up in Galloway and elsewhere in Scotland, has an entry for Thread o'Blue, "any little smutty touch in song-singing, chatting, or piece of writing." Farmer ["Slang and Its Analogues Past and Present," 1890] offers the theory that this meaning derives from the blue dress uniforms issued to harlots in houses of correction, but he writes that the earlier slang authority John Camden Hotten "suggests it as coming from the French Bibliothèque Bleu, a series of books of very questionable character," and adds, from Hotten, that, "Books or conversation of an entirely opposite nature are said to be Brown or Quakerish, i.e., serious, grave, decent."[blue etymology, blue origin, 英语词源]
chat (v.)youdaoicibaDictYouDict
mid-15c., "talk idly, babble," short for chatter (v.). Meaning "to converse familiarly" is from 1550s. Sense of "flirt with, ingratiate oneself with" (in later use often with up (adv.)) is from 1898. Related: Chatted; chatting.
chatty (adj.)youdaoicibaDictYouDict
"fond of chatting," 1746, from chat + -y (2). Related: Chattily; chattiness.
chitchat (n.)youdaoicibaDictYouDict
also chit-chat, 1710, diminishing reduplicated form of chat. The verb is attested from 1821. Related: Chitchatting.