"the naming ceremony of the new catapult"

Once again, we see Frank’s love of ritual. He has to name the catapult, and the ceremony is a sort of initiation ceremony – the catapult is “baptised” with Frank’s fluids, thereby embalming them with his power. A baptism is a sacred ritual used by the church, in particular Christian churches, that uses water to initiate a person as a member of the Church. It is a symbolic cleansing, and just as a priest would baptise a child, Frank has "baptised" his new catapult, initiating it into his service.