“Beverage”…very nice word, but have you ever heard someone actually say, “I would like a cold beverage.”?
“Shall”…another nice English word, and other than in the UK, you will never hear an American say, “I shall call you in the morning.” Same goes for the negative, “we shan’t be late for the party”.
I use shall all the time. (And despite my bog Irish heritage, I use it correctly.)
I use ‘beverage’ occassionally.
I never say “shall” because in all honesty, I don’t know the difference between using “shall” in a sentence and using “will.”
As for other words I never hear anyone say (aside from Alex Trebek on Jeopardy) is “potable.”
Both of those words are used regularly in contexts more formal than standard, everyday speech. They are widely understood even if most people never feel the need to use them.
If you want obscure words, the verbophiles here will be more than happy to oblige you. The two that sprung to mind when I read the title were ‘extirpate’ and ‘cwm’, both English words. English has a nigh-infinite amount of inkhorn words.
Which is probably a better title to this thread and what I was trying, for no particular reason, to express.
Words people understand, but don’t really use.
Extirpate is rare? I’ve used it. And I’ve heard “cwm” before, but only in reference to weird English words. That one might have currency in Wales, but it never made it across the pond.
(BTW: the old myth about shall and will - I can never remember which one you use with the first person, and which you use with the second and third - is not a rule that ever existed in any dialect of English. It’s a fiction like the whole splitting infinitives thing.)
Excalibre, we’re a pretty literate bunch and I know we use words most people never hear. I, for example, haven’t heard or read the word ‘extirpate’ in a long time. Prevalence in normal communication decides how rare a word is.
As for ‘cwm’, I happen to like that word and bring it up as often as possible. 
Well, I’ve never heard or seen the word ‘cwm’ before but I plan to use it regularly. Once I find out what it means.
Then there are those words that should exist,but no-one ever uses them just their opposite.All those things that are shevelled or wieldy or ert…
Unlike “beverage” or “shall”, there are some other words that have quite obvious meanings but are almost never used. I don’t think anyone will run to a dictionary to find out waht advertently means but have you ever heard anyone use it?
Iceland_Blue
Great minds think alike but some type faster than others.
Cwm is not an English word , it is Welsh and means valley. On the Welsh language TV station there is a long running soap opera called Pobol y Cwm (people of the valley). This is quite popular even among non Welsh speakers, as there are English sub-titles.
“Cwm” is quite popular with crossword puzzles and their makers.
What about words that we only use one tense/one category (not the correct word, but it’s early and the mind hasn’t kicked in yet)?
Example: we use the word “oblivion”, but do we use the verb “obliviate”? Not really. Maybe “obliviated”. Words like that…
That has left me completely whelmed… 
Do bastardised words count. For example, back in school the word brethren was bastardised to “bredrin” to talk about friends. My geeky self prefers brethren.
‘cwm’ is borrowed from Welsh, but you can’t say it is not an English word. It is part of the English lexicon just as ‘cafe’ and ‘schlep’ are, even though they are borrowings from French and Yiddish, respectively.
I think the only people who borrow *cwm * are crossword compilers. Unlike cafe and even schlep , I have never heard it used here in the ( non Welsh part) of the UK. Further , I think the only reason it is a favourite amongst cross-word buffs is that it is a word with no vowel. So its use outside Wales is entirely artificial.
Touché.
The major route up Mount Everest is a valley called the Western Cwm.
Hundreds of weird words here: