stoolien.

1924 G. C. Henderson Keys to Crookdom 419 Stool pigeon, a spy, stoolie, squealer. One who betrays his fellow crooks.

1930 ‘E. Queen’ French Powder Myst. p. xiv Without the stool-pigeon a huge percentage of felonies would remain unsolved... Our problem is to find a ‘stoolie’ who will part with the tip.

1947 Sun (Baltimore) 13 Sept. 8/1 Victor Mature..succeeds in winning sympathy for Nick against odds, overcoming even the stigma which attaches to the stoolie.

1958 ‘E. McBain’ Killer's Payoff (1960) viii. 79 The policeman trusted the stoolie's information... The stoolie trusted the policeman... Cops were averse to working with pigeons they did not know and trust.

1960 ‘E. McBain’ See them Die v. 48 You'd stool on Pepe for that rotten cop?.. A stoolie is a stoolie.

1974 T. P. Whitney tr. A. Solzhenitsyn Gulag Archipel. I. i. iii. 128 ‘There is no way out! You have to confess to everything!’ whisper the stoolies who have been planted in the cell.

1978 LaRosa & Tanenbaum Random Factor (1979) 60 When Parker put the pressure on, some stoolie somewhere would turn the man he was looking for.