There are phrases and sayings that are difficult to trademark, although some have tried to do so, because they are in common use. Mostly, if a trademark is approved, it is because the use of the word is limited, specific, and confined to a certain context: such as a clothing brand, or a series of novels by a certain publisher.
It would seem that a quick-on-the-draw innovator cannot sit on a lovely, useful (or even useless) word and make a fortune from harassing hapless folks who happen to use it. One probably could not trademark "absquatulate" (https://dictionary.cambridge.org/us/dictionary/english/absquatulate), a word that has fallen out of general use. It is a pompous word for "leaving" with mildly scatalogical undertones. It makes me think of a military man suffering from an exotic tummy bug, getting up suddenly from his place around the campfire, and rushing into the darkness downwind of his fellows.
"THE TROUBLE WITH THE" is probably a nothingburger. Legal bloggers Ashley J. Heilprin and Andrew W. Coffman for the law firm Phelps Dunbar LLP discuss the trademarking of the definite article by The Ohio State University for use in connection with their brand for sports apparel.
One cannot protect a word without context, and one cannot trademark a design. One can protect a brand.
For anyone who might be confused or outraged or alarmed that someone can trademark "THE", this is a very well-written and helpful article covering the entire issue, and much more from what a trademark is, to what rights exist and what do not, to why anyone would go to the trouble and expense.
"A trademark or a service mark is a word, phrase, symbol or design that identifies the source of goods or services. When applying for the “THE” mark in 2019, The Ohio State University originally submitted a shirt with the word “THE” and the school’s logo prominently displayed across the chest as its specimen..
The Trademark Office found that the specimen did not show the use of the word “THE” as establishing a source of goods, but was merely an ornamental design. A design on a T-shirt is not normally protected as a trademark. Instead, what is protectable is the brand itself. The Ohio State University then offered a second specimen that included “THE” not in the design of the shirt, but on the tag. Generally, the Trademark Office considers brands on tags as evidence that consumers associate the mark with a single source of goods."