Green’s Dictionary of Slang

conversation n.

[conversate v.; note Shakespearian and later euph. conversation, sexual intimacy, e.g. Satirist 15 July 1832: ‘The noble Lord was amusing himself [...] in close conversation with a rural beauty’]

(US black) a romantic ‘line’, used for the purposes of seduction.

[US]G. Smitherman Black Talk.

SE in slang uses

In compounds

conversation fluid (n.) [it ‘lubricates’ conversation]

(US) illicitly distilled whisky.

Mexico Wkly Ledger 8 Feb. 3/2: Scarcely two days after he had been liberated [...] he again acquired a bundle of conversation fluid.
[Aus]C.M. Russell Trails Plowed Under 55: I get a little of that conversation fluid in me.
[US]R.F. Adams Cowboy Lingo 228: The Westerner’s names for whiskey were legion [...] ‘conversation fluid’.
[US]R.F. Adams Western Words (1968) 38: Conversation fluid – Whiskey.
Foxfire Fall–Winter 101: Various names given moonshine include: [...] conversation fluid.
‘Cowboy Vocabulary’ at 🌐 WHISKEY: barleycorn, base-burner, bug-juice, coffin-varnish, conversation-fluid, [etc.].
conversation water (n.) [it ‘lubricates’ conversation] (US)

1. beer.

[US]Daily Trib. (Bismarck, ND) 23 Oct. 4/1: Beer is ‘conversation water.’.
[US]Shiner Gaz. (TX) 23 Nov. 8/1: We had plenty of quail and doves and a keg of conversation water.
[US]New Ulm Rev. (MN) 27 Mar. 5/4: Walter had spent the greater part of his day in filling up on conversation water.
[US]Arizona Republican (Phoeniz, AZ) 21 Sept. 16/2: Miller was loaded to the guards with conversation water.
[US]A. Baer Two & Three 6 Feb. [synd. col.] The old conversation water is mute, stabbed by its own corkscrew.

2. champagne.

[US]Bismarck Trib. (ND) 23 July 8/1: Charlie Williams handles the ribbons on the quarter stretch [...] while his extensive patronage handle the ‘conversation water’.
[US]Ade Breaking Into Society (1904) 34: The highest-priced Caterer in Town would deal out the sparkling Conversation Water as if Brut and Buttermilk cost about the same.
[US]Durant Wkly News (OK) 23 July 4/3: Campaign cigars seem to be out of fashion this year, and the ‘conversation water’ is a thing of the past.

3. (US) illicitly distilled whisky.

[US]Dly Ardmoreite (OK) 26 Dec. 8/2: ‘Casinghead’ is Name of Brand New Brand of Conversation Water [...] which seems to have a kick like a Missouri mule.