I would like to know if you are aware of more words which are uncommon, yet possess a very simple meaning and have a sort of air of obscurity about them. So far I know:
Albeit - though
Sans - without
Know anymore words which fit with these "category of their own"? In a pivate project I am doing they may actually be quite helpful
defenestration - the action of throwing someone out of a window.
exsanguine - bloodless or anaemic
fugacious - transient or fleeting
mimsy - rather feeble and prim or over-restrained
@Grey Wolf
Defenestration is the action of throwing something out of a window. Though the most famous examples in history do involve defenestrating people, LOL. Even if it was from the ground floor.
@Rascake
Have you considered looking on the web or over at English.SE?
Duthomhas, I know there are definitions for "the action of throwing someone or something out of a window" but I like the original use to mean throwing someone out of a window...seems funnier somehow.
(and I like the OED https://en.oxforddictionaries.com/definition/defenestration)
There's a difference between the "uncommon vocab" of some posts, and Rascake's examples in the OP. I think, for Rascake, the point is that words like "sans" do simply mean "without", but can only be used properly in a much narrower way, and is likely to make the speaker sound pretentious or fake (unless you're Shakespeare).
Other vocabulary can have different connotations that aren't as simple as a thesaurus suggestion would make them. But also, for example, "eschew" doesn't necessarily just mean "abstain from", it also has the connotation that you're shunning it, in my experience at least. You don't eschew a piece of chocolate if you're allergic, you eschew things like violence.
Anyway, you might find some interesting entries if you search for words that are "archaic". That won't encompass all the words you're looking for, but it will be some of them.