– a discovery imagined to be important but proving worthless
– a disordered situation
This expression is first recorded in Galateo of Maister Iohn Della Casa, Archebishop of Beneuenta. Or rather, A treatise of the maners and behauiours, it behoueth a man to vse and eschewe, in his familiar conuersation A worke very necessary & profitable for all gentlemen, or other. First written in the Italian tongue, and now done into English by Robert Peterson, of Lincolnes Inne Gentleman (1576), the translation by Robert Peterson (floruit 1576-1606) of Trattato nel quale, sotto la persona d’un vecchio idiota ammaestrante un suo giovanetto, si ragiona de’ modi che si debbono o tenere o schifare nella comune conversazione, cognominato Galateo overo de’ costumi (1558), by the Florentine author Giovanni della Casa (1503-56). In this text, mare’s nest translates Italian marauiglia, marvel, and means illusory discovery:
Running and going in the streat and other such gestures.
I would not haue a gentleman to runne in the streate, nor go to fast: for that is for lackies, and not for gentlemen to doe. Besides that, it makes a man weary, sweate, and puffe: which be very vnsightly things for suche men to doe. I would not yet haue a man go so softe and demurely, as a maide or a wife. And when a man walkes, it is no good sight to see a man shake his bodie to muche, nor to hold his hands bare and emptie: nor yet cast & sting his armes vp & downe, in such sort as a man would weene, hee were soweing of Corne in the field: nor Stare in a mans face, as if he had spied a mares nest.
The synonymous expression horse-nest is first attested in A floorish vpon fancie As gallant a glose vpon so triflinge a text, as euer was written (1577), by Nicholas Breton (1555?-circa 1626):
The Vssher follie first, [...]
To laughe at a horse nest, and whine too like a boy,
If any thing do crosse his minde, though it be but a toy [= a foolish fancy].
In Fraser’s Magazine for Town and Country of November 1837, the reviewer of the 93rd volume of Dr. Lardner’s Cabinet Cyclopædia, criticising “all the slovenliness of haste, and all the confident presumption of ignorance” with which this volume was executed, wrote:
It would be a wonder if the erudition of this work were not on a par with its writing, and that the mares’-nests of its discovery were amply suited by the flea-bittenness of its style.
The American writer Jean Stafford (1915-79) used the expression in the sense of an untidy mess in Children Are Bored on Sunday, a short story first published in The New Yorker in February 1948:
Emma herself had been hunting for the Botticelli all afternoon, sidetracked first by a Mantegna she had forgotten, and then by a follower of Hieronymus Bosch, and distracted, in an English room as she was passing through, by the hot invective of two ladies who were lodged (so they bitterly reminded one another) in an outrageous and expensive mare’s-nest at a hotel on Madison.
In an article titled The Lords’ amendments on the Test Acts published in The Examiner of 27th April 1828, the journalist who reported the discussions at the House of Lords on the Repeal of the Test Acts (i.e. various acts directed against Roman Catholics and Protestant Nonconformists) coined a punning variant of mare’s nest:
On Thursday, [...] Lord ELDON smelt a Popish Plot in some apparently very orthodox words of the preamble, and proposed a declaration of Protestantism. The House took time to consider the danger, and the necessity of the proposed substitution, and adjourned to Friday [...] to consider the ELDON discovery of a Popish night-mare’s nest.