@danvolodar
We're not talking about baptism, we're talking about baptising which is not just about administering the specific rite of baptism. Baptise can be used in other contexts where it means cleaning or purifying or giving a name. It comes from the greek word baptizo which means to immerse and there's no specification as to what is being immersed. Heck, in French, we familiarly use the expression baptising milk or wine to refer to diluting them with water, so the term can certainly be used for objects and the meaning will clearly differ.
In the context of this manga, the holy objects have names and are not treated as mere objects, as they "choose" their wielder. The baptised armour might very well simply refer to an object that was blessed through a religious rite, that was given a name and that through the process gained some essence that made it much more than just armour. Baptise seems to be about the right word to describe all that.