In his 1988 book Rennes-le-Chateau: Le dossier, les impostures, les phantasmes, les hypotheses, Gerard de Sede affirmed that Boudet wroteLa Vraie Langue Celtique in a cryptic fashion, adding that he used Jonathan Swift's A Discourse to Prove the Antiquity of the English Tongue, Showing from various instances, that Hebrew, Greek, and Latin were derived from English (1712) as a guide.
This work by Swift is absolutely hilarious. And why wouldn't Boudet adopt this style of pun to encode his 'secret of a local mystery at Rennes-les-Bains'. After all he studied the English Language to degree level. He obviously loved the English language and what you could do with it. I think I know why Boudet adopted this language - after reading Simon Miles it is obvious that to decipher his MAP you need to understand English.
But how did Gérard de SÈDE know that Boudet used the work of Swift?