Brian: My two cents worth - found when googling.

"Baptism vs Christening
In the discussion of baptism vs christening, it is important that one understand that traditionally one event is always a religious ceremony, while the other may or may not have a religious connotation. Baptism is the infant ceremony that is always religious and has its ties to ancient Christianity and even Judaism. Christening on the other hand, while it may be religious, can also be performed as a non-religious naming ceremony.
Infant baptism, although a Christian ceremony, is not practiced by all denominations. Those denominations that practice infant baptism are the more orthodox such as Roman Catholic and the Protestant denominations, such as Lutheran, Anglican, Presbyterian and Methodist, just to name a few."

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"Baptism - the ceremony or sacrament of admitting a person into Christianity.
Christening - the act or ceremony of baptizing and giving a name to an infant."