There's a somewhat old-fashioned turn of phrase in US English, "You don't know shit from Shinola".
Shinola was a particularly popular brand of shoe polish, and thus the intended implication of the phrase being that the target of the remark was too ignorant to be able to tell the difference between shoe polish and actual excrement.
Over time, at least in my neck of the woods growing up, the association resulted in the word "shinola" itself becoming a common bowdlerization of the word "shit", sometimes on it's own, sometimes in other phrases (I distinctly recall a relative once uttering the phrase "up to your neck in shinola", and you can be sure they didn't mean boot polish.)
The linguistic irony of all this is that over time, many speakers did, in fact, come to be unable to recognize "shit" from "Shinola", as the brand fell on hard times and disappeared but the saying lingered in memory out of context.
I myself didn't learn that "Shinola" was an actual brand of anything until years later in adulthood, and so as a kid, I was always rather confused why the saying seemed to be comparing two kinds of the same thing. I chalked it up to the way a lot of common idioms become corrupted and redundant in strange ways over time.
And now, of course, I reckon many speakers not as old as I am would not recognize any form of the phrase, which is perhaps why some galaxy-brained venture capitalist in Texas has bought the brand Shinola out of whatever disused file cabinet it had been laid to rest in, bought up a bunch of property in Detroit, and set about building a watch and bike factory and trying to launch a luxury brand.
A luxury brand whose brand name is, or at least was, literally synonymous with shit. There are, in fact, Shit stores, selling Shit watches, Shit bikes, Shit leather goods, Shit pet supplies, and you can even book a room in the Shit hotel.
And they have, remarkably, somehow been successful, particularly with politicians. Bill Clinton, David Cameron, disgraced Michigan governor Rick Snyder, and motherfucking Barack Obama are all allegedly big fans of Shinola watches, despite all of them being at least old enough to be able to recognize the idiom. Perhaps they appreciate the personal irony.
Language is fascinating. Brand language, it seems, is a whole other plane.
I think another favorite detail of this is that of all the dozens of products they've since slapped the name on, not one of them is a shoe polish, the one thing that might give the viewer context as to what the name "Shinola" was originally meant to invoke.