Green’s Dictionary of Slang

croaker n.4

[? croaker n.2 i.e. the price; or croaker n.1 ]

(Aus./US) a newspaper.

[US]Matsell Vocabulum.
[US]Trumble Sl. Dict. (1890).
[US]Dly Dispatch (Richmond, VA) 1 Nov. 3/3: Thieves [...] have no use for a ‘croaker’, or a newspaper that ‘gives them away’.
[Aus]Baker Popular Dict. Aus. Sl.