Well my source is a Linguistics Textbook (Language Files, 11th Edition, p15-16) but it says that these changes happened as late as the 17th and 18th centuries because Scholars considered written Latin to be the ideal language (likely because most historical works had been translated to Latin at some point). So even though ending sentences in prepositions had been common for centuries in spoken English, that became frowned upon because it was not allowed in Latin.
Specific examples in the book of "rules" applied to English to match written Latin include:
- Don't ending sentences in prepositions
- Don't split infinitives
- Don't use double negatives
The chapter as a whole was actually about linguistic prescriptivism, but the Latin examples are pretty interesting nonetheless. 17th and 18th century seem pretty far past the point at which French would be the big influencer, but there's no doubt French did influence English as well (though more vocab it seems).
Specific examples in the book of "rules" applied to English to match written Latin include:
- Don't ending sentences in prepositions
- Don't split infinitives
- Don't use double negatives
The chapter as a whole was actually about linguistic prescriptivism, but the Latin examples are pretty interesting nonetheless. 17th and 18th century seem pretty far past the point at which French would be the big influencer, but there's no doubt French did influence English as well (though more vocab it seems).