[somozasayre]

One assumes that by "Christendom" you mean "Chrismation". In an case the Christian name is given in Baptism (it is only given in Chrismation if Baptism is presumed to be already accomplished - but that's a different discussion). The name is given by the priest, however, the instructions that I have for priests stipulates that the priest should abide by the decision of the parents in choosing a name for a child. If you are an adult who is converting, usually you are the one to tell the priest what name to use. My strong preference and advice is to use whatever name you have been given as long as it is an acceptable Christian name. If the first name is not useful, then go for the middle name. If that doesn't work then start looking for "sound alikes" or "equivalent meanings". If for some reason none of the above work, then I strongly suggest that you avoid "unique" names or "odd sounding" names. Use something that will wear well in daily use.

Fr David Moser