It is custom in Europe to refer to the first name as the "Christian" name, since it is the one given at Baptism.
But, what was meant here by "Christian" name is a little more exact. Basically meaning names found in the Bible, or names of famous saints. In other words, traditional names passed down through the common Christian heritage.
By naming a child, you wish to impart some imprint on him. To try to make some character of the saint part of your child.
Just making up a name, or using one from a commercial product, is to make a mockery of this.
SD