Green’s Dictionary of Slang

(Aus./US) a newspaper.

1859		Matsell Vocabulum.
1881		Trumble Sl. Dict. (1890).
1882		Dly Dispatch (Richmond, VA) 1 Nov. 3/3: Thieves [...] have no use for a ‘croaker’, or a newspaper that ‘gives them away’.
1895		Crowe Aus. Sl. Dict. 21: Croakers, newspapers.
1941		Baker Popular Dict. Aus. Sl.