word for today "quiddity"

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.

Quiddity comes from the scholastic Medieval Latin term quidditas, "essence," from quid, "what."

[from dictionary.com]

& of course, there's a 4th meaning, as any Clive Barker fan will tell you.