Green’s Dictionary of Slang

(US gang) to talk; to gossip; to malign.

1943		‘Whitman College Sl.’ in AS XVIII:2 Apr. 153/2: catting. Gossiping, making disparaging remarks.
1949–51		in M. Daly Profile of Youth 109: Next day she ‘catted’ to one of her friends that ‘he’d better not think I’m going to take streetcars’.
1953		W. Brown Monkey On My Back (1954) 99: Cat was also employed as a verb meaning to talk, while digging the cat meant talking aimlessly or at length.
1960, 1975		Wentworth & Flexner DAS.