Metagrobolized

Meaning: Mystified, confused. Cotgrave has:

To dunce upon, to puzzle, or (too much*) beat the braines about.

Usefulness: 1

Logofascination: 1 (A Rabelaisian formation from the Greek mataios, vain or frivolous, and a French term, grabeller, which Cotgrave defines as "To garbell spices &c. (and hence) also, to examine precisely, sift neerely, looke narrowly, search curiously, into." I like the fact that the spelling of garbell is itself garbled into grabeller.)

In the wild: It's in Stalky and Co! That's right, this blog has allowed me to connect Sir Thomas and Kipling, albeit via Rabelais. 'The Impressionists' features this line: "Come to think of it, we have metagrobolised 'em."

Calepinerie

Meaning: An old French word, Cotgrave defines it as:

A true, just, and precise interpretation, or translation of every single word.

Usefulness: 2 (It must be pointed out that 'a true, just and precise interpretation' and a 'translation of every single word' are rarely the same, as you'd know if you'd spent any time over at God Didn't Say That.)

Logofascination: 1 (Calepinus was a lexicographer, and his name lived on for several centuries in various words. A calepin was a dictionary and then a notebook in both English and French, after his Latin dictionary. As discussed further below, "Calepinus recensui" was apparently used as a sign-off by copyists.)

Quiddity

Meaning: Quintessence. Thisness. The defining feature. The vibe, and various other hand-wavy concepts.

Usefulness: 1 (particularly in hand-wavy conversations)

Logofascination: 2 (comes with bonus synonym, haecceity)