Inpulregafize

Meaning: The context suggests thinking hard or becoming confused, but no-one except Sir Thomas knows what this means, or its origins.

Usefulness: 1 ("Don't inpulregafize yourself, sir, we'll fix it." "She's easily inpulregafized, isn't she?)

Logofascination: 1 (Sir Thomas probably invented it to match Rabelais' 'emburelucoque', which Cotgrave defines as "Turmoiled, blundered, or pestered, as the braine about a troublesome businesse."  The etymology for inpulregafize is obscure, which is probably why it is still undefined.  It is possible that just this once Sir Thomas invented a word without Latin or Greek elements, but I think that's unlikely.  I might need to email some classicists.)

In the wild: Nope.

Tutivillus

Meaning:  Depending on the era/writer, Tutivillus is the devil responsible for collecting the words of gossips, to be reported against them in heaven, or the errors priests made in liturgy*, ditto. He is also referred to as the "patron demon of scribes", causing errors such as haplography. As is appropriate, his name has any number of possible spellings, including Titivullis. There's more about him here, here or here.

Usefulness: 1 (However scanty the evidence for his past existence may be, we need a typo demon.)

Logofascination: 1 (After various roles in the Mystery Plays, he evolved into a word, titivil, and allegedly shows up twice in Shakespeare as tilly-vally or tilly-fally. That's quite a career, particularly when you consider what small errors it is built on - Screwtape would be impressed.)

Saliency

Meaning: Salient, or obvious - originally meant leaping, and then sticking out, and is, I think, slowly evolving from obvious into meaningful.  Invented by Sir Thomas Urquhart's contemporary, Sir Thomas Browne, whose words, while not nearly as stylish as Sir Urquhart's, seem to be more generally used.

Usefulness: 3

Logofascination: 3 (but only because it's etymologically leaping)