If the people mocking him are knowledgeable enough, they might liken him to Father Athanasius Kircher, SJ, who in those years was perhaps one of the preminent codebreakers and one of the first scholars to attempt deciphering Egyptian hyeroglyphs. This is not necessarily a slight; possibly the modern equivalent of calling someone an Einstein. It might be a compliment or a slander, depending.
Another likely candidate for a likeness would be Borrino, vulgar name for Joseph Francis Borri, Esq., a pictoresque and at times unsavory quack that graced the second half of the seventeenth century. Not universally known, though. To dub someone a Borrino gesuita should have been slight enough to warrant a death duel (Borrino hasn't a very nice sound in Italian even if one didn't know it was used as meaning little Borri).
At that time, "jesuit" was a not too affectionate nickname for the members of the Society of Jesus, for they were expected to "find Christ in all things".