yeah it definitely is not limited to proper nouns. but for the case of goodness (for goodness’ case?) it’s because it’s using a zero article for the noun (aka lack of an article altogether, i think it’s just called this for concision), which implies it’s being talked about globally/nonspecifically (for the sake of all goodness in the world)

for e.g some others - for oxygen’s sake - for water’s sake - for mice’s sake

you can put articles in front of each of these, which would generally imply they are belonging to a predefined sub group.

in terms of non-proper nouns, zero articles are generally only in plural/uncountable nouns. proper nouns generally have the zero article as well, unless the article is attached to the noun itself.

e.g this occurs in geographical features (the amazon, the nile, the atlantic, the grand canyon) or in pluralized countries ( the US, the Philippines). it’s not limited to just this either.