I'm an Anglcan priest (=Episcopalian, if you're American), retired but active. 'Christening ' was originally the anointing element of the rite, part of which was associated with the naming, whereas baptism is the immersion in or pouring over of water. 18th and 19th century RC baptism records are always in Latin, but then, so was the liturgy. Jacobus was an official name, but then James was the official name in English, and yet Jim would be the most used form in practice: which was the 'real' name? At my mother's (Anglican) baptism her first name was first written as Margaret, but then corrected to Marguerite; my grandmother was Eleanor, bur the Vicar wrote Helena, and the family called her Nellie or Nell. A 17th century ancestor was Samuel, but the Vicar recorded him as Shemuel, in accordance with the Hebrew. Such are the pitfalls of using baptism registers!