I read the novel to see if it had any new spin on stuff I had already read from the book Holy Blood, Holy Grail in the 80's. It put forward that whole san greal ---> sangreal ---> sang real argument bit if I'm not mistaken. The source for all those "revelations" was supposedly a member of Priory of Sion. The document that was used to support its existence was hoaxed.
IIRC, the oldest legends of the holy grail are roughly from about the same time frame as the Arthurian ones and from that same part of the world. So why would you be looking for hidden meanings in the word in Swahili? Urdu? or to the point, French?
The "messages" in Davinci's paintings was a new take. If you look at the actual Davinci paintings mentioned in the book though, you see that their trying to read way too much into them - like some of the supposedly subliminal messages in WTs, ads, etc.
I think the author of this novel, must have had some idea of the flaw in just sticking with the sang real bit. So he tried to show a connection of the original chalice with Magdalene by way of the motifs of the blade and the chalice in the Sacred Feminine ( Honestly though, I wouldn't be suprised if he misportrayed even those symbols).
As a novel, I did come to like the character of Silas.