I restricted my search to 'eat shit', although I included that phrase with the variant spellings 'shite', 'sh*t', 'sh-t', and 's--t', where possible. I also included the various inflections of 'eat'.
A troublesome instance in Supplemental Nights, 1888 (R.F. Burton), returned from a search for 'eat shite', footnoted "to eat skite" (as meaning "to talk or act foolishly") in reference to text reading "devour ordure":
The OED Online does not give 'skite' as a variant spelling of 'shite'.
The earliest unalloyed figurative use I uncovered was from a novel titled The Folded Leaf, published in 1945. This text clip is the excerpt from Google Books results:
The next appearance was not visually verifiable, as it occurred in a "restricted rights" novel about life in the infantry, Toward an Unknown Station (Allan Lyon), published in 1948:
"You eat shit," Ben told him. "Goldbricking while I work my ass off!" We all helped him hide his cache, and then we settled down happily to wait for chow, thinking of the stolen feast we would enjoy later in the afternoon.
Regarding the appearance of 'shit' (absent 'eat') in print prior to 1900, J. Wright, in The English dialect dictionary, volume 5 (EDD), compiled a fair-sized collection of dialect uses from the 1600s through the 1800s, some dated. These are clippings of the primary entries:
Nowhere in Wright's collection, neither in Volume 5's main entries nor in Volume 2's entries for 'eat', did I find the 'eat shit' phrase.
Eric Partridge, in his annotated 1963 edition of the third edition of F. Grose's A Classical Dictionary of the Vulgar Tongue (full text not available; the link is to the 1796 edition of Grose), provides a good summary of the use of 'shit' in the early 1900s. In the snapshot below this paragraph, Partridge's historical summary begins with "--In 1914-1918 ...", and his summary of the senses found in EDD appears after "--Dialect has many ...". The surrounding material in Partridge's annotation is based on information from the Oxford Dictionary (OD).
Regarding other negative results, the phrase 'eat shit' did not appear in my searches of
- The Slang Dictionary, 1865 (Hotten)
- The American Slang Dictionary, 1891 (Maitland)
- A dictionary of slang, jargon & cant embracing English, American, and Anglo-Indian slang, pidgin English, gypsies' jargon and other irregular phraseology, 1897 (Barrère)
- A new dictionary of the terms ancient and modern of the canting crew, in its several tribes, of Gypsies, beggers, thieves, cheats, &c., with an addition of some proverbs, phrases, figurative speeches, &c., 1899 (Gent)
- A new dictionary of Americanisms; being a glossary of words supposed to be peculiar to the United States and the dominion of Canada, 1902? (Clapin)
- A Dictionary of Slang and Colloquial English, 1921 and 1909, original issue 1890 (Farmer & Henley; I checked both the abridged, 1921, and the seven-volume revised edition, 1909)
Of those, I could expect with a reasonable degree of certainty that if the phrase 'eat shit' had much currency in English prior to the 1900s, it would've been likely to appear in Farmer & Henley.
Altogether,
- the absence of the phrase 'eat shit' in Wright's apparently comprehensive dialect collection,
- as well as Partridge's failure to mention the phrase in his annotation of Grose,
- along with the phrase's non-appearance in any of the six other sources in the bulleted list (including especially Farmer & Henley),
- and the OED's earliest attesting quote being 1955 (unless you count 'crap' in 1930),
suggest that, with the troublesome exception of Burton's footnote, the earliest appearance in print of 'eat shit' may be the use in the 1945 novel, The Folded Leaf.
Nonetheless, it is unreasonable to suppose that 1945 use is, in fact, the earliest appearance of the phrase in print; the 1945 use is merely the earliest print appearance I could uncover with a limited set of resources.
Further, aside from appearance in print, the use of the phrase 'eat shit' in dialectal speech before the 1900s, even dialectal speech in antebellum Virginia, is not unreasonable--merely unlikely.
Best Answer
They are adjective phrases. An adjective phrase is a group of words that describe a noun or pronoun in a sentence. The adjective phrase can be placed before, or after, the noun or pronoun in the sentence.
http://examples.yourdictionary.com/adjective-phrase-examples.html