Green’s Dictionary of Slang

1. advantage, luck, resource.

1859, 1860		Hotten Dict. of Modern Sl. etc.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor I 259/2: That’s my cokum (advantage).
1864, 1867, 1870		Hotten Sl. Dict.
1882		Sydney Sl. Dict. (2 edn) 2: Cocum - Shrewdness, ability, luck.

2. knowledge, cunning; thus do the cocum, fight cocum, being cunning, artful, usu. in illegal contexts.

1845		Era (London) 7 Sept. 11/4: The youth who is surnamed Adam, in consequence of the depth of his cocum.
1850		Man of Pleasure’s Illus. Pocket-book n.p.: [I]f you do the coakham, and tumble to the slum, you may fake the duck in rumbo style.
1857		‘Ducange Anglicus’ Vulgar Tongue 9: cocum [...] To fight cocum, to be wary.
1860		Hotten Dict. of Modern Sl. etc. (2nd edn) 119: ‘To fight cocum,’ to be wily and cautious.
c.1863		gloss. in Occurence Book of York River Lockup in Seal (1999) 36: I have got the yacks so do not come to fight cocum.
1873		Sl. Dict. 124: Cocum shrewdness, ability, luck; “Jack’s got COCUM, he’s safe to get on, he is,” ― viz., he starts under favourable circumstances; “to fight COCUM” is to be wily and cautious.
1876		C. Hindley Life and Adventures of a Cheap Jack 37: It was necessary to use a little judgment, and instead of attempting to fight them it would be far better to ‘fight cocum’.
1877		Queenslander (Brisbane) 10 Mar. 21/1: We have the ‘cokum’ to appreciate the selectors’ usefulness.
1881		Newcastle Courant 9 Sept. 6/5: With the aid of his friends and his own ‘cocum,’ he made his peace with his mistress.
1882		Sydney Sl. Dict. (2 edn) 2: Cocum - Cunning and sly. To Fight Cocum - To be wary.
1895		Crowe Aus. Sl. Dict. [as 1882].
1904		Sydney Sportsman (Surry Hills, NSW) 16 Nov. 1/1: [T]he success he attains is solely attributable to the bit of ‘kokum’.
1938		Williamstown Chron. (Vic.) 26 Nov. 2/3: Mr Badman showed some ‘kokum’ when he decided to leave the Stardrift horse in the care of Bob.

3. sense.

1865		Leaves from Diary of Celebrated Burglar 6/1: Very few honest people entered this house, as it was a well known resort of the Leeds ‘cross’ [...] and that it was bad ‘cocum’ to go there.
1887		Cumberland Mercury (NSW) 8 Oct. 6/6: Nobbs showed his usual ‘kokum’ in leaving the chair before the ‘fun’ began on Saturday.
1900		Sydney Sportsman (Surry Hills, NSW) 28 Nov. 1/1: It proves them as not having sufficient cokum not to know when they are making first-class omadhauns of themselves.
2006		Guardian 6 Mar. 🌐 Common cokum [...] meant Tessa Jowell telling her husband long ago that ‘I have to comply with these ministerial code provisions – is there anything I need to know?’.

4. (also kokum) deceit, entrapment (through pretending to sympathy/kindness); thus give someone kokum, to deceive.

1886		Portland Guardian 27 Oct. 2/7: Is the old fellow going to surprise us, and is it all ‘cokum’ about his leg? Spare my days, he gallops — yes, gallops.
1889-90		D. Sladen in Barrère & Leland Sl., Jargon and Cant I 528/1: Kokum (Australian prison), sham kindness.
1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.] 92: KOKUM-KID-TAFFY: leading or coaxing on, giving him kokum.

5. (S.Afr. Und., also chochem) a thief, usu. an intelligent one.

1963

L.F. Freed Crime in S. Afr. 106: A ‘chochem’ is a thief or crook who considers the risks involved in a robbery.