From the Websters dictionary 1905 edition: "A barbarous term used in school philosopy for essence" - gotta love a dictionary with that degree of vitriol.
My intended career was as an academic in philosophy. My chosen field was logic and the structure of consciousness, especially with reference to linguistics and mathematics.
One of my heroes is Willard van Orman Quine, who was a logician at Harvard.
http://en.wikipedia.org/wiki/Willard_Van_Orman_Quine
One of Quine's books is titled "Quiddities". I rather liked the term so when I established my consulting company I called it Quiddity Technical Services.
I don't like monikers but Audiogon insisted that I register as a business and that I take a moniker which referred to my business name, so there you have it.
Mark Kelly