I subscribe to this but usually already know the word - however here is something new to me (and it looks like a great Scrabble word!)
quiddity \KWID-ih-tee\, noun:
1. The essence, nature, or distinctive peculiarity of a thing.
2. A hairsplitting distinction; a trifling point; a quibble.
3. An eccentricity; an odd feature.
He wanted to capture not just live animals, but the
aliveness of animals in their natural state: their
wildness, their quiddity, the fox-ness of the fox and the
crow-ness of the crow
--Thomas Nye, quoted in "Ted Hughes, 68, a Symbolic Poet
And Sylvia Plath's Husband, Dies," New York Times,
October 30, 1998
So far, I have tried to intimate, through meshed parallels
and contrasts, something of the nature, the quiddity, of
Japanese and of American literature.
--Ihab Hassan, "In the mirror of the sun: reflections on
Japanese and American literature, Basho to Cage," World
Literature Today, March 1, 1995
Boswell set biography a new ambition: capturing the
copiousness and quiddity of a personality -- the self
peculiarly revealed in odd quirks and, especially, in
unpredictable, evanescent talk.
--John Mullan, "Dreaming up the Doctor," The Guardian,
November 11, 2000
It is neither grammatical subtleties nor logical
quiddities, nor the witty contexture of choice words or
arguments and syllogisms, that will serve my turn.
--Michel de Montaigne, "Of Books"
She has looked after my interests with consummate skill,
dealt with my quiddities and constantly kept up my spirits.
--John Brewer, The Pleasures of the Imagination
I began . . . to give some thought to the memoir I had
promised to write and wondered how I would go about it --
his freaks, quiddities, oddities, his eating, drinking,
shaving, dressing and playfully savaging his students.
--Saul Bellow, Ravelstein
Quiddity comes from the scholastic Medieval Latin term
quidditas, "essence," from quid, "what."