One who helps solicitors to affidavit men, or false witnesses.—’I wish you had, Mrs. Crump;’ a Gloucestershire saying, in answer to a wish for any thing; implying, you must not expect any assistance from the speaker. It is said to have originated from the following incident: One Mrs. Crump, the wife of a substantial farmer, dining with the old Lady Coventry, who was extremely deaf, said to one of the footmen, waiting at table, ‘I wish I had a draught of small beer,’ her modesty not permitting her to desire so fine a gentleman to bring it: the fellow, conscious that his mistress could not hear either the request or answer, replied, without moving, ‘I wish you had, Mrs. Crump.’ These wishes being again repeated by both parties, Mrs. Crump got up from the table to fetch it herself; and being asked by my lady where she was going, related what had passed. The story being told abroad, the expression became proverbial.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
See also the definition in Nathan Bailey's 1736 dictionary of canting and thieving slang.
Crummy * Crump-backedNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes