Green’s Dictionary of Slang

1. (UK Und.) lice; thus chat parade, a delousing session.

c.1698		B.E. Dict. Canting Crew.
1719		A. Smith Lives of Most Notorious Highway-men, etc. (1926) 204: Chats, lice. Squeeze the chats, i.e., crack or kill those vermin.
1725		New Canting Dict.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict.
c.1750–1882		B.M. Carew Life and Adventures.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: Chatts, lice, (cant) perhaps an abbreviation of chattels, lice being the chief live stock or chattels of beggars, gypsies, and the rest of the canting crew.
1812		Vaux Vocab. of the Flash Lang.
1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc. 24: Chatts — i.e. Chattels, abbreviated — Lice.
1846		Swell’s Night Guide 65: You staggs my queer togs, and thinks I’m chatty; but Lord love you! I never had a chat in my mortal days. [Ibid.] 72: I’ve copped some nob-rangers, and I arnt got no chat-rake; so I shall snuff ’em out.
1852		Kendal Mercury 17 Apr. 6/1: Blow me [...] if that ken of Beggar-me-Out’s vasn’t crammed full of chats (lice) and hoppers (flies).
1859		Matsell Vocabulum.
1867		W.H. Smyth Sailor’s Word-Bk (1991) 181: Chats. Lice. Also lazy fellows.
1870		Hotten Sl. Dict. 97: CHATTS, lice.
1885		Dly Gaz. for Middlesborough 6 Nov. 3/4: Twenty-seven of us in one room, most of us dirty [...] Then the ‘flats’ and ‘chits’ [...] Suffice it to say that they were at (sic) work, and I was awake the whole night through.
1916		Rising Sun 25 Dec. 8/2: Why waste all that ration jam [...] add a little fat— / And we could use it well, / In killing off the chat.
1917		A. Wright diary 15 Aug. in Muddy France (1988) 12: Had a lengthy ‘chat parade’, and a bath.
1919		Aussie (France) 11 Feb. 11/1: When in the trenches one gets used to chats, as you blokes know, and looks upon them the same way that a dog regards fleas. They keep a fellow from worrying about his other worries.
1921		(con. WWI) E. Lynch Somme Mud 51: Dark and I get out of our underpants and pull them on again, inside out, to trick the chats [...] We chance the chats about our upper regions.
1925		(con. WWI) Fraser & Gibbons Soldier and Sailor Words 52: Chat, A: Vermin, in particular a louse.
1931		E. Blair letter 4 Sept. in Complete Works X (1998) 228: As to new words, here are some [...] Chat = a louse.
1936		Western Mail (Perth) 11 June 2/5: There was a bottle of dope in the corner that they used for chats [...] Three or four others took off their flannels and strides and sprinkled some in the seams.
1940		Western Mail (Perth) 30 May 2/3: Chats soon became too common to take notice of.
1967		‘Whisper All Aussie Dict.’ in Kings Cross Whisper (Sydney) xxxiii 4/3: chat: A prison bed-bug.
1974		Adamson & Hanford Zimmer’s Essay 99: Orwell gives ‘chat’ as a term for ‘louse’ [...] In New South Wales prison argot, it means both ‘louse’ and a certain type of prisoner.
1999		G. Seal Lingo 59: Many of these terms are still used. On Gallipoli the Anzacs soon made the acquaintance of body lice, or chats, a term also common in US folk speech.
2024		J. Meades Empty Wigs (t/s) 618: ‘Diabolical itchy like chats all over you it were. Worse than these patches’.

2. (Aus. teen) as defined by a sharpie n.² gang, a victim, a pariah.

2004

(con. 1960s-70s) T. Taylor Top Fellas 21/1: The lowest of the low were called ‘Chats’. [...] In sharp lingo it meant a paraiah, in for a hiding.