Green’s Dictionary of Slang

1. (also barb) to clip the edges of gold coins.

1610

Jonson Alchemist I i: I’ll bring thee [...] thy neck / Within a noose, for laund’ring gold, and barbing it.

2. (UK Und.) to cheat.

1865

Leaves from Diary of Celebrated Burglar 51/2: That mean ‘barbering’ Curley has been hanging round him all the time.

3. (orig. UK Und.) to rob, to steal; thus hotel barber under hotel n., a thief who specializes in robbing hotel guests.

1865		Leaves from Diary of Celebrated Burglar 7/2: I have been ‘barbered’ by some one while I was asleep, and every bloody ‘mag’ in my ‘kick’ is ‘namassed’.
1867		Bell’s Life in Sydney 27 Apr. 6/4: it is quite common for a well-dressed thief to take apartments in an hotel and ‘barber’ all the inmates; in other words, to get up in the night, visit all the rooms, and steal as much as possible. This, in technical language, is called ‘Dancing a lunching-drum’ .
1901		W.S. Walker In the Blood 143: ‘Barbering’s’ just a screaming farce to me.
1904		Sydney Sportsman (Surry Hills, NSW) 12 Oct. 4/2: [D]ozens of ‘mugs’ are ‘barbered’ by them weekly.
1909		Truth (Brisbane) 10 Oct. 12/7: [S]ome of his fancy boarders had barbered me as clane as the day I was born.
1926		Truth (Perth) 27 Feb. 8/3: They were arrested in the act of ‘barbering’ the fashionable assembly in an hotel ballroom recently [ibid] 8/7: Sometimes the dips ‘barber’ a friend of the authorities, and have to work back the loot before the afternoon is done.
1967		‘Whisper All Aussie Dict.’ in Kings Cross Whisper (Sydney) xxxii 6/1: barber: To steal from vacant rooms in hotels.

4. (US) to gossip, to chatter; thus barbering, conversation [ref. to the loquacious SE barber, who chatters as he gives customers a ‘trim’].

[1920		R. Lardner Big Town 21: The other gent and my two gals was talking like barbers].
1929		D. Hammett ‘Fly Paper’ Story Omnibus (1966) 57: What the hell am I doing barbering with a lousy dick?
1932		(con. 1910s) J.T. Farrell Young Lonigan in Studs Lonigan (1936) 63: They barbered about nothing in particular.
1936		R. Chandler ‘Guns At Cyrano’s’ in Red Wind (1946) 235: Let’s not barber. We got business to do.
1949		R. Chandler Little Sister 178: How much longer we have to barber around with this monkey?
1962		Ragen & Finston World’s Toughest Prison 790: barbering – Conversation.
1962		B. Veeck Veeck — as in Wreck 125: I called down to the locker room and asked [baseball stars] Boudreau and Feller to dash over and barber with them [i.e. out-of-town fans] until the train came.