Green’s Dictionary of Slang

buck n.4

[Hind. बक (bak), noun, chatter, babble, बकना (baknā), verb, to chatter, talk nonsense]

talk, conversation, esp. when garrulous or irritating.

‘Tom Harkaway’ ‘Sequel to Sport in the Worst Station in Bengal’ in India Sporting Rev. Sept. 109: [L]ots of buck and jaw and great champing of jaws, terrible scrambling for the best pick of the eggs and lots of laughing; so we spent a jolly half hour.
[UK]B. Patterson Life in the Ranks 140: Some of the ‘knowing blokes,’ prominent among whom will be the ‘grousers’, will [...] be ‘arguing the point,’ ‘chewing the rag’, or ‘fat’, ‘giving the old buck’.
J.D. Gordon Work and Play in India and Kashmir 191: ‘After dinner Charlie and I had a long ‘buck’ – Anglice, ‘chat’ – which consisted mainly of long deep growls at the weary monotony of bachelor life in Gurrumpore’.
[Ind]P.C. Wren Dew & Mildew 117: He was just having his chota hazri and we had a ‘buck’ over it.
[UK]R. Tressell Ragged Trousered Philanthropists (1955) 450: Why should we put up with a lot of old buck from the likes of ’im!
[UK]W.L. George Making of an Englishman III 299: As I wasn’t having any of his old buck we said a tearful farewell, I don’t think.
[UK]‘Sapper’ Third Round 640: If you or I went round to have a buck with a fellow, we should remember whether the isolation was complete.
[UK](con. WWI) Fraser & Gibbons Soldier and Sailor Words 37: Buck: (Hind.—Bâk). Exaggeration. Too full of talk.
[UK]S. Murphy Stone Mad (1966) 43: ‘No more old buck out of you, now,’ said Nedgill.
[UK]G.W. Target Teachers (1962) 179: ‘If I have any buck from any of ’em [...] I’ll cook ’em in a stew for tomorrow’s dinner.’ All the children laughed.
[Ire]J. Morrow Confessions of Proinsias O’Toole 78: Any more of yer oul’ buck and I’ll start picking the tar off you now.
[UK]Barltrop & Wolveridge Muvver Tongue 95: Cheekiness and back-answering is ‘old buck’.

In phrases

put in buck (v.)

(UK Und.) to testify (poss. as a perjurer) on someone’s behalf.

[US] ‘Scene in a London Flash-Panny’ Matsell Vocabulum 98: Whew! I know the kiddy like a copper, and I saved him once from lumping the lighter by putting in buck.