Faciendas

Meaning: Sir Thomas helpfully defines this for us:

Faciendas, are the things which are to be done; faciendum is the gerund of facio.

Faciendum and agendum have similar (if not identical*) meanings, but agendum's busy plural moved with the times and assumed a new meaning.

Usefulness: 1 (If you want a short meeting, ask if anyone has any faciendas. Alternatively, The Horologicon suggests facienda as a more interesting name for a to-do list.)

Logofascination: 1 (Etymologically facienda and hacienda are the same word. Note that Sir Thomas adds the English plural s to the already plural Latin word, although he then uses the singular faciendum a few paragraphs later. He's done this before, so I've added a label for his Latin plurals.)

Enodandum

Meaning: Sir Thomas kindly provides definition and etymology in the Lexicidion at the end of Trissotetras:

that which is to be resolved and explicated, declared, and made manifest; from enodo, enodare, to unknit, or cut away the knot. 

Usefulness: 1 ("What is my first enodandum for the day, Alex?" In the quote below, Sir Thomas pluralises it as enodanda but then adds the English s as well: enodandas.)

Logofascination: 1 (While this is not yet in the dictionary, enode - to loose or untie; enodous - free from knots; and enodable - capable of being freed from knots; are all in the OED, and should be used more often.)

Data

Meaning: information, pieces of information

Usefulness: 2 (it's not very exciting, but we keep using it, so it must be useful.)

Logofascination: 1 (because, and only and wholly and solely because, Sir Thomas has the first citation for this word in the OED. He used it in 1645, forty-six years - yes, forty-six - before the next citation*. See graph below for evidence of how ahead of the curve Sir Thomas was on this one.  Some guy is cited under datum from 1630, in a text called Most Easie Way Finding Sunnes Amplitude, which is clearly an early example of spam.)