I was just reading that the other day when looking for something in that book and you totally reminded me. Love that quote from Churchill. I believe some of those rules came from forcing grammatical rules from Latin onto English, but I can't recall the specifics. Another book somewhere, I'm sure.
As language users, we sometimes get into difficulty when we must follow prescribed language rules. This usually occurs in writing. Spoken language is much more informal than writing and less constrained. In the nineteenth century, formal grammar guides were written, often prescribing rules used by the upper classes. As a result, today we are saddled with the distinction in formal writing between who and whom, the incorrectness of using since to mean because, the inadmissibility of the split infinitive, and the not ending a sentence with a preposition rule. Regarding the latter, Winston Churchill quipped, "That is the type of arrant pedantry up with which I shall not put."