What is the libellous meaning of ‘daffy-down-dilly’?

Question

In Dorothy L. Sayers’ novel Unnatural Death, the barrister Mr Towkington advises Lord Peter Wimsey to be careful to avoid libel:

‘You are too easily surprised,’ said Mr Towkington. ‘Many words have no legal meaning. Others have a legal meaning very unlike their ordinary meaning. For example, the word “daffy-down-dilly”. It is a criminal libel to call a lawyer a daffy-down-dilly. Ha! Yes, I advise you never to do such a thing. No, I certainly advise you never to do it.’

_{Dorothy L. Sayers (1927). Unnatural Death, chapter 14. London: Ernest Benn.}

What is the libellous meaning of ‘daffy-down-dilly’? The Oxford English Dictionary says only:

daffydowndilly, n. 1. A daffodil; used at first in the generic sense. Still a widespread popular name of the Yellow Daffodil. 2. A shrub: probably the Mezereon, which is still so called in Yorkshire ‘from the slight similarity of the Greek name Daphne with Daffodil’ (Britten and Holland).

And Eric Partridge adds another meaning, equally unhelpful:

daffy-down-dilly. A dandy: ca. 1830-80. Leman Rede in Sixteen-String Jack.

_{Eric Partridge (1923). A Dictionary Of Slang And Unconventional English, p. 204. London: Routledge.}

Answer 1

TL;DR: A ‘daffy-down-dilly’ is a lawyer who engages in double dealing, that is, representation of both sides in a case, for his own advantage.

The reference is to a case reported in Rolle’s abridgment of the Common Law:

Si home dit al un Counceller del ley en le North, Thou art a Daffa-down-dilly. Action giſt ove averrment que les parols ſignifie que il eſt un Ambedexter, Mich. 10 Car. B.R. En Peares Caſe dit d’eſtre adjudge en Scaccario, & agree per curiam.

_{Henry Rolle (1668). Un Abridgment des plusiers Cases et Resolutions del Common Ley, volume I, p. 55. London: A. Crooke et al.}

This was translated into English by Knightley D’Anvers:

If a Man ſays of a Counſellor of Law in the North, Thou art (g) a Daffa-down-dilly an Action lies, with an Averment that the words ſignifie that he is an (h) Ambodexter. Mich. 10 Car. B. R. in (i) Peare’s Caſe, ſaid to have been adjudged in Scaccario, and agreed per Curiam.

(g) So if he calls him Ambodexter. Dal. 97. cited Moor 409. ſaid Godb. 214. adjudged.

(h) B is a good Attorney, but that he will play on both Sides, actionable; 1. Brownl. 5. per Curiam, tho’ Judgment was given againſt the Plaintiff for a Fault in the Declaration.—He is a Paltry fellow, for he deals on both Sides, and deceives them which put him in truſt; actionable being ſpoke of an Attorney. Noy 11. adjudged niſi, Yelv. 32 adjudged.

(i) Cart. 214. S.C. cited. Noy 98. S.C. cited.

_{Knightley D’Anvers (1705). A General Abridgment of the Common Law, volume I, p. 113. London: John Walthoe.}

This meaning of ‘ambidexter’ is in the OED:

ambidexter, n. and adj. 2. Law. A corrupt lawyer (or occasionally juror) who takes fees or bribes from both sides in a case. Now historical.