I wonder where the author learned English - there are a lot of words and phrases in this article/book that I’ve never heard before! To simper, adoration, put on airs, amorous, interlocutor, etc
https://books.google.com/ngrams/graph?content=simper%2Cadora...
Over time your vocabulary gets much wider. I have native English speakers asking me where I got certain words from because they are not often used spoken.
Another trick is when you write look up synonyms instead of using the same word over and over again.
But in the words you dropped I learned at least 1 new one. To simper :)
My favourite new word I learned is from "Malazan Book of the Fallen": "susurration" [0], a word that, in my experience, even many native speakers don’t know, yet is uniquely beautiful (to me).
these are just Latin derived words.
But if he is French and that is connected to the Latin hence he had good(weird?) vocabulary. English vocab is also mostly derived from Latin.
"80% of the words in the English dictionary are Latin derived."
amorous, etc...
it's no surprise, as you say... every word op listed is Latin root and French too.