My father was originally a country boy, born in Australia at the beginning of the 20th century.
He had a number of typically Australian expressions (e.g. "stone the crows"), but the one I remember most was "you lie like a dog in straw".
He always used this as a friendly jibe of disbelief when someone in the family was obviously trying to fool him with some story. I was quite young when I figured out the play on words inherent in this expression, which is why I've remembered it so well. However, every reference I can find in a preliminary search of the internet has a shortened version "you lie like a dog" which, among other things, has lost its early rural association (i.e. the availability of straw).
My question then: does anyone know of a documented use of the 'full' expression as handed down to me by my father, or of any other references to this version? (which, to me, has an air of earlier authenticity).
Best Answer
Early lying like a dog
The root expression seems to have been simply "lie like a dog." The earliest match for the phrase that an Early English Books Online search turns up is from George Whetstone, The Right Excellent and Famous Historye, of Promos and Cassandra Deuided into Two Commicall Discourses (1578):
Here "lye lyke a dogge" seems to mean something like "tell untruths as with as little conscience as a dog has."
From Austin Saker, Narbonus: The Laberynth of Libertie (1580):
The lying here appears likewise to refer to dissembling, as it does again in "A Merry New Song How a Bruer Meant to Make a Cooper Cuckold and How Deere the Bruer Paid for the Bargaine" (1590?)
The sense is also unmistakable in the next example, although it is then taken wrongly (as a jest) by the second party to the quoted dialogue. From John Taylor, A Dog of War, or, The Trauels of Drunkard, the Famous Curre of the Round-Woolstaple in Westminster His Seruices in the Netherlands, and Lately in France, with His Home Returne (1628):
From very early times, then, speakers were conscious of the competing meanings of lie as "tell an untruth" and "position oneself horizontally."
Nevertheless, some early instances refer simply to literal or figurative placement in a demeaning position. For example, from Richard Fowns, Trisagion or, The Three Holy Offices of Iesus Christ, the Sonne of God, Priestly, Propheticall, and Regall How They Ought of All his Church to Be Receiued (1618):
The earliest match for lying like a dog in something involves a manger, consistent with the information that Laurel provides in a comment above. From Thomas Dekker, The Honest Whore with, the Humours of the Patient Man, and the Longing Wife (1604):
This usage seems to be intended literally as the behavior of a lazy dog; there is no hint here of dishonesty. To my surprise, I could not find another instance of "lying like a dog in a manger"—which would seem closely akin to "lying like a dog in straw"—after Dekker's until this instance in a speech by Representative Bertram Podell of New York titled "France: Faithless Ally and Betryer of Israel," in The Congressional Record (January 8, 1969):
As in this instance, the familiar trope of "a dog in a manger" generally focuses on a very different type of behavior: denying something that is of no use to oneself to others who could benefit from it.
Meanwhile, "lying like a dog" in the "telling falsehoods" sense does appear in a variety of longer phrases, including "lie like a dog licking a plate" (sometimes rendered as "lie as fast as a dog will lick a plate"), "lie like a dog on a rug," "lie like a dog a-trotting," and "lie like a dog running on hot sand."
The association of lying (in the sense of telling falsehoods) with dogs evidently occurs in languages besides English. John Williams, The Rise and Progress of the Northern Governments; viz. the United Provinces, Denmark, Sweden, Russia, and Poland, volume 2 (1777) describes a judicial punishment against calumniators that, he says, is "still practiced in Poland":
Update (May 10, 2021): Even earlier lying like a dog
Bartlett Whiting, Proverbs, Sentences, and Proverbial Phrases from English Writings Mainly Before 1500 (1968) has an interesting entry for "lie like a dog" that includes five citations from approximately the period 1300–1420:
The ineteresting thing about these early instances is that all of them seem to focus on lying dead in the open—that is, unburied—like a dog.
Lying like a dog in straw
I couldn't find any instances of this expression in newspaper or book databases online. The closest expression that I did find is from Walter De La Mere, "The Creatures," in The London Mercury (January 1920):
The simile in this case is to a dog resting in a nest of straw. There is no sense that the narrator's nodding amounts to a falsehood, but that he is building a cocoon of caution around himself rather than responding to the other speaker's candor with openness of his own.
Conclusion
I could not find any instances of "lie like a dog in straw" in the various online book and newspaper databases I checked. The expression may be used in pockets of the English-speaking world today, and its usage may go back a considerable distance into the past, but it hasn't left a trail that I could discover.