Faith in these half-remembered and poorly formed “rules” has become just that: a strong belief or trust in something that you can’t explain or prove. Saying “For which room are these the keys?” is demonstrably not the only natural way to formulate this question.

There is often a not-too-subtle corollary that others don’t care, or don’t know, or were not educated. Like so many markers of class, it becomes a signifier of “us” as opposed to “them.”

This rule also is very easy to remember and identify (like split infinitives), and it exposes social aspects of learning and pedantry. Showing you know this “rule” means showing that you are among the group of people who care in this particular way about language.

That’s why we have these non-rule “rules” about things like terminal prepositions or split infinitives. They are engrained in our sense of aesthetic choices, which are choices for style and usage. They are not mandated by grammar.

So “grammar” moved on. But although scientific analysis clarified organic elements of English grammar, they did nothing to change the more subjective qualities of “eloquence,” which had been by then sitting on three centuries of following Latin’s example.

It wasn’t until the field of linguistics separated from literary studies in the late 1800s that languages began to be re-analyzed according to their true natures. By the time modern linguists looked at this problem, they came to the correct conclusion: “What problem?”

As an aside, these are different from phrasal verbs. But the fact that phrasal verbs create sentences with adverbs at the end helps to explain why both constructions sound so comfortable to English speakers:

Latin has such a hold on prestige and privilege that it is still used for things like college diplomas. It’s not surprising that invoking the ancient authority of Latin seemed to be the correct thing to do in academic contexts, like the teaching of grammar.

But, just as dictionaries through the years looked at earlier dictionaries, grammar books looked at earlier grammar books. So this “rule” that ending a sentence with a preposition, natural in English and impossible in Latin, was perpetuated. <split infinitive enters the chat>

But we must remember that, everything Dryden had read in school as a model of literature was in Latin. So, at our distance today, we can see that he was making an aesthetic judgment and calling it a grammatical error. From his point of view, Latin grammar WAS Latin eloquence.