Over the years, dogs have been subjected to incredibly bad press linguistically speaking so it comes as no surprise that the phrase “sick as a dog” goes back several hundred years.
Voltaire — the pen name of François-Marie Arouet — was born November 21, 1694 to a middle class family. As a child and through his whole life Voltaire was always ill. In a letter dated 1732 written to his friend Tieriot, Voltaire wrote:
My health and my affairs are shaken to an incredible degree. I was not born to live in a city. There is no health for me save in the solitude of La Rivière; I feel as if I were in hell when in this wretched city of Paris. I finish by assuring you I am as sick as a dog, in other words, the most unfortunate creature in the world.
But in August 1592, playwright and dramatist Robert Greene — a colleague of William Shakespeare — over-indulged in Rhenish wine Robert and pickled herrings while dining with his friend, Thomas Nashe. For a month afterwards, Greene was very ill — which eventually led to his death — and while sick, Gabriel Harvey penned the following ditty:
A rakehell, a makeshift, a scribbling fool:
A famous bayard in city and school.
Now sick as a dog, and ever brainsick:
Where such a raving and desperate Dick?
Historically Speaking 