Yes, those units are called 'semantic primes/primitives': https://en.wikipedia.org/wiki/Semantic_primes

Thank you for the reference.

>Another practical step could be to identify a specific minimal set of language units required for any given popular nonconstructed language. Is this already a thing?

You mean something like this question?

https://news.ycombinator.com/item?id=19331307

Presumably, that would depend on your conversatonal goal. We could refer to the Apollo lander as a spacecar[0] in a casual conversation but that could be tedious or misleading if a NASA representative were trying to pigdin with an ESA representative about the metal casing of a booster rocket ballooning past the expansion tolerance of the o-rings, using only the 3000 most common english words.

[0] https://xkcd.com/1133/

> We could refer to the Apollo lander as a spacecar[0]

This seems to be reaching for exoticism for the sake of exoticism, given that the standard term is the metaphorically identical "spaceship".

It can't even be justified by the restriction to "the 3000 most common words", since ship is #1208 in COCA.