Green’s Dictionary of Slang

chickee! excl.

also chickie! chicky!
[chicken n. (2a), i.e. one is acting in a cowardly manner]

(US) a warning of the impending approach of authority – whether police officer, parent or teacher – and thus a command to stop whatever one is doing that might cause that authority to act against one (cf. chiggers! excl.).

[US]H. Roth Call It Sleep (1977) 86: Chickee de cop, behin’ de rock. De monkey’s in de ba’ba shop!
[US]S. Kingsley Dead End Act II: Guard ’at watch and lay chickee! [Ibid.] dippy, milty and angel dash to the hopper, all yelling ‘Chickee!’.
[US]J.G. Rothenberg ‘Peanuts! The Pickle Dealers’ in AS XVI:3 Oct. 190: Pootso! Knocko! Bootz! Pootz! These four [...] are warnings, corresponding to the obsolete Chickee! and Cheese it!
[US]‘Hal Ellson’ Tomboy (1952) 142: Chickie, the nabs!
[US]Goldin et al. DAUL 43/1: Chicky or Chiggers. Beware! Look out! Police!
[US]Mad mag. Nov. 7: Chickee! Looketh who comes!
[US]B. Wohl A Cold Wind in August (1963) 183: ‘Chickee!’ They froze at the signal [...] a white-topped police car pulled slowly to a stop.
[US]Wentworth & Flexner DAS.
(con. 1915–25) Lutz Collection n.p.: Chicky! A word of warning. It was the usual word among school children (about 1915–1925) in Ramsey [NJ], when warning others of the approach of a teacher or the principal; [...] It meant that one should stop whatever behavior the authorities would condemn.
[US]H. Rawson Dict. of Invective (1991) 80: Kids also cry chickie as warning, but this is when they lay chickie acting as lookouts.

In phrases

lay chickie (v.) (also lay chic, ...chick, ...chickee, keep chickie, keep chips, stand chickie)

(US) to maintain a lookout (during a crime).

[US]H. Roth Call It Sleep (1977) 342: ‘And stay hea a secon’, see! – I’ll lay chickee.’ He crept warily up the stairs.
[US]J.G. Rothenberg ‘Peanuts! The Pickle Dealers’ in AS XVI:3 Oct. 189: To lay pootz, To lay bootz. To keep watch; to be a grapevine; to lay chickee.
[US]‘Hal Ellson’ Tomboy (1952) 13: I’ll go in first, Mick follows me and you lay chick.
[US]W. Brown Monkey On My Back (1954) 127: Luis [...] would go down the line of parked cars trying the doors while Hector ‘lay chic’.
[US]W. Brown Teen-Age Mafia 76: Long before he was old enough for the brand he laid chick for the roving gangs.
[US]C. Brown Manchild in the Promised Land (1969) 32: Not having anyone to lay chickie for me, I had to do it [i.e. a theft] quicker.
[US] in S. Harris Hellhole 221: You’ll come along to stand chickie for the cops.
[US]E. Grogan Ringolevio 46: He [...] stole a [...] hard-top Oldsmobile convertible while Clearhead and Girsch kept chickie for him.
[US]H. Rawson Dict. of Invective (1991) 80: Kids also cry chickie as warning, but this is when they lay chickie acting as lookouts.
[SA]R. Malan My Traitor’s Heart (1991) 53: Robin [...] kept chips for the fuzz.
play chickie (v.) (also play chicky)

(US) to maintain a lookout; usu. during a crime.

J. Petracca Come Back to Sorrento 59: ‘You stand up against the door and play chickie.’ [...] ‘I’ll play chickie, but I ain’t in on it!’.
[US]P. Thomas Down These Mean Streets (1970) 75: Three of us went in for the bread; Crip stayed behind to play chicky.
[US]N. Heard Howard Street 67: They searched for a money belt [...] while Butch and Brother played chickie.
[US]E. Torres Carlito’s Way 59: I’ll play chickie on the stoop.
V. Lindner Outlaw Games 93: I will play chickie for another dude and his woman in the john, but it does not give me no satisfaction.
D.W. McCullough Think on Death 238: I’ll watch the door, play chickie-the-cops in case they turn up.
(con. 1960s) W. Flores Foundling 119: Either one of us can play chickie while the other enters the room and collects the loot.