Green’s Dictionary of Slang

to talk privately.

1859		Hotten Dict. of Modern Sl. etc.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor I 251/1: The trio at this stage of the performance began ‘puckering’ (talking privately) to each other in murdered French.
1864, 1867, 1870		Hotten Sl. Dict.
1891		Birmingham Dly Post 31 Mar. 3/5: He would talk ‘padding ken’ (lodging-house) slang [and] ‘pucker cant’ (‘talk cant,’ or slang).
1934		P. Allingham Cheapjack 320: Pucker (Romany) – To talk.