Green’s Dictionary of Slang

1. a bedfellow, usu. a female one [post mid-19C use is US].

1610

Beaumont & Fletcher Scornful Lady I ii: In this word ‘necessary’ is concluded all that he helps to man; woman was made the first, and therefore here the chiefest.

2. a lovers’ go-between.

1678

Behn Sir Patient Fancy IV i: I have a sort of a matrimonial Kindness for a very pretty Woman [...] and last night she made me an Assignation in her Chamber: when I came to the Garden-door by which I was to have admittance, I found a kind of Necessary call’d a Baudy Waiting-Woman, whom I follow’d.

3. an outhouse, a privy.

1786		C. Morris ‘The Great Plenipotentiary’ Collection of Songs (1788) 45: For fancied Delight, they all clubbed for a Shite, / To Frig in the School Necessary.
1801		Sporting Mag. June XVIII 161: The suit of an architect who [...] had built for him no less than six water closets. The plea [...] in defence was that of nonage. This plea, observed a legal wag, must be unavailing, as minors are compelled to pay for necessaries.
1810		in N.E. Eliason Tarheel Talk (1956) 284: One of the public Necessaries.
1842		in N.E. Eliason Tarheel Talk (1956) 284: The necessary on the lot . . . is a nuisance in the immediate neighborhood in which it stands.
1851		in N.E. Eliason Tarheel Talk (1956) 285: He built a ‘necessary’.

4. money.

1837		Roscommon Jrnl 16 Sept. 2/1: The applicant posted the necessary.
1881		Northern Trib. (Cheboygan, MI) 5 Nov. 3/1: ‘Let’s take a nip.’ ‘Have you got the necessary?’.
1897		Daily News 6 Sept. 3/6: A fund ... for the purpose of providing the ‘necessary’ in order to bring test cases .
1911		Sport (Adelaide) 11 Nov. 6/4: A number of Parkside girls are on the look out for new boys—but none without the ‘necessary’ to hire motor-cars need apply.
1918		Aussie (France) 7 Sept. 7/1: If you were stiff, you could be sure that he would come to light – when he had the necessary. But this latter seldom lasted more than forty-eight hours after the ghost had walked.
1956		J. Thompson ‘The Cellini Chalice’ in Fireworks (1988) 87: You haven’t raised any of the necessary elsewhere?
1959		J. Gosling Ghost Squad 124: The story was put across as only Cooper could do it, and at the end of two hours the American parted with the necessary.
1961		Rigney & Smith Real Bohemia xx: The addict makes a payment in advance for the drugs (‘fronts the necessary’).
1968		D. O’Grady A Bottle of Sandwiches 21: There was enough of the necessary left to fill our forty-four with juice.
1986		C. Bowles G’DAY 25: Everyone needs moolah. If you haven’t got The Necessary they repo your wheels and turf you out of your fibro. So everyone needs a lurk.

5. what is required, e.g. intelligence.

1947		P. Newton Wayleggo (1953) 149: His cries for a reviver were so pitiful that we conducted an exhaustive search for a drop of the necessary.
1993		Smith & Noble Neddy (1998) 263: Now Murray is good when it comes to ideas, but he hasn’t got the necessary when it comes to executing a plan.