cover-up, n. — Green’s Dictionary of Slang

cover-up n.

1. a concealment, usu. illegal or at least unethical; also attrib.

1928		Phila. Eve. Bulletin 5 Oct. 40/3: Here are a few more terms and definitions from the ‘Racket’ vocabulary: [...] ‘cover-up house,’ a place used by permitees to divert alcohol to bootleg channels.
1938		R. Chandler ‘Red Wind’ in Red Wind (1946) 52: If I don’t get my cover-up, you don’t get your dough.
1942		R. Chandler High Window 203: Your mother still thinks Linda took the doubloon and that your story [...] was just a cover-up to protect her.
1952		W.R. Burnett Little Men, Big World 136: ‘I was saying,’ said Red, ‘that my hair’s not carrot colour if there isn’t a cover-up going on.’.
1967		N. Dunn Poor Cow 110: He’d got a building job as a cover up.
1976		J.W. Dean III Blind Ambition 357: The cover-up had been a stupid error. Lying about it had been deadly for [Nixon]. [...] He’d been caught in his lies, so why didn’t he confess?
1981		J. Ellroy Brown’s Requiem 235: He’s got kind of a cover-up going.
1998		I. Welsh Filth 336: A pathetic cover-up job.
2000		Indep. 10 Jan. 2: The Conservatives also accused the government of a ‘cover-up’.

2. (US Und.) a criminal’s associate, a confederate.

1949

Monteleone Criminal Sl. (rev. edn).

In phrases

cover-up man (n.)

(US und.) a man who walks or stands with a street prostitute poses as her legitimate partner to the police; he disappears when she is approached by a customer.

1935

Afro-American (Baltimore, MD) 18 May 15/1: Ladies of the pavement and their ‘cover-up man’ will soon provide work for the gendarmes.

do a cover-up (v.)

(US black) to provide an alibi, i.e. for a mixed-race couple.

1935

E. Freeman ‘The Whirling Hub’ in Afro-American (Baltimore, MD) 6 Apr. 15/1: Can you imagine an ofay doing a cover-up for a sepia guy who was playing an ofay gal?