"That white-haired bloke... Gerard? Gerwant?" — The actual name of this subject is conjectural or unknown.
A "secret temple language" is known to at least certain clergymen of the Nordling Pantheon, as well as some mages. It is used, among others, to code secret messages and formulate incantations.
Geralt of Rivia once learned an "exorcism" in this language from some priestesses of Huldra, but its meaning turned out to be a vulgar joke.[1]