The term pigeon’s milk, also pigeon milk, denotes an imaginary substance which, as a joke, a child or gullible person may be sent to buy.
The English antiquary and topographer John Brand (1744-1806) recorded it in the appendix to Observations on popular antiquities: including the whole of Mr. Bourne’s Antiquitates vulgares, with addenda to every chapter of that work: as also, an appendix, containing such articles on the subject, as have been omitted by that author (1777):
A Custom, says the Spectator, prevails every where among us on the First of April, when every Body strives to make as many Fools as he can. The Wit chiefly consists in sending Persons on what are called sleeveless* Errands, for the History of Eve’s Mother, for Pigeon Milk, with similar ridiculous Absurdities.
* Skinner guesses this to mean a lifeless Errand. I am not satisfied with this Etymon. He assigns no Cause for his Conjecture.—This Epithet is found in Chaucer.
In A Classical Dictionary of the Vulgar Tongue (1788 edition), Francis Grose wrote:
Pigeons Milk. Boys and novices are frequently sent on the first of April to buy pigeons milk.
He also recorded the following, possibly related, expression:
To milk the pigeon; to attempt impossibilities, to be put to shifts [= to be brought to extremity] for want of money.
An article titled April Fools, published in The Westmorland Gazette of Saturday 5th April 1823, mentioned
the embryo wits who send literal tools on sleeveless errands; such as to borrow “The History of Adam and Eve’s father and mother”—to purchase “a bottle of pigeon’s milk,” or “a pint of stirrup oil.”
And The Scots Magazine of April 1824 published the following in The First of April; “All-Fool’s-Day”:
The practice is wearing out; and practical jokes, on this particular day, are become less frequent than formerly; for I can recollect the time when half the people in my native village were employed in either making April fools, or being made so themselves. I have known a lubberly boy sent a wild-goose chase of many miles, and of several hours’ duration, from his being the bearer of a letter containing merely the words, “Send the gowk another mile.” Young girls were sent for a pound of maidenblushes¹, or a bottle of pigeon’s milk.
(¹ maiden’s blush, or maiden blush: a delicate pink colour)
The term pigeon’s milk also designates as a curd-like secretion from a pigeon’s crop with which it feeds its young. In Ornithologia, or The Birds: A Poem, in Two Parts; with an introduction to their natural history; and copious notes (1828), James Jennings wrote:
The crop of the Pigeon is peculiar, consisting of two divisions; the secretion in which, at certain times, is not less peculiar than its structure. It appears, that as soon the young Birds are hatched, a whitish ash-coloured fluid is there secreted, both in the male and female, in abundance, with which they feed for some time the young before they feed them with grain; so that, although Pigeon’s milk would be considered a solecism, yet this fluid seems to be very much like milk its properties.
The meaning of pigeon’s milk is obscure in the following advertisement, published in The Suffolk Chronicle; Or, Weekly General Advertiser, and County Express of Saturday 17th July 1813:
TO SHOEMAKERS, LADIES, &c.
Of Ipswich and Vicinity.
B. AND M.
PRESENT their most respectful compliments, and beg leave to inform them, they are just returned from London with a large and fashionable assortment of all kinds of shoemakers’ kit, consisting of knives, awls, tacks, [illegible word], wax, pigeon’s milk, straps, [illegible word], and handcuffs, such as are in use from the beginning to the end of the trade, and which they are enabled to sell on the most reasonable terms, being the remaining stock of a deceased Duchess.