Is the term "Christian name" in decline in British English?

The decrease in usage of the expression "Christian name" may be a reflection of the cultural changes that happen through time. It, however, didn't necessarily refer to religion, according to the following extract:

• Traditionally, a christian name or baptismal name is a personal name given on the occasion of Christian baptism, with the ubiquity of infant baptism in medieval Christendom. In Elizabethan England, as suggested by Camden, the term christian name was not necessarily related to baptism, used merely in the sense of "given name":

  • "Christian names were imposed for the distinction of persons, surnames for the difference of families."

• In more modern times, the terms have been used interchangeably with given name, first name and forename in traditionally Christian countries, and are still common in day-to-day use, although today, the secular term 'first name' is considerably the most common.

(Wikipedia)

Usage notes:

From The AHD:

• Because it presupposes that an entire society is Christian, the term Christian name when used generically can be taken as offensive in diverse societies. Writers seeking a way to avoid this problem can use first name or forename instead.

From The Collins Dictionary:

• Christian name was often loosely used to mean any person's first name as distinct from his or her surname. Nowadays, especially in official documents, alternatives which do not refer to a particular faith, and are therefore more inclusive, are often used: first name, forename, and given name.

I'm a Brit in my late 40s, so heading towards that bah, in my day... old fogey demographic that you mention (perish the thought).

I sometimes use "Christian name" out of sheer habit, but my (somewhat large) irreligious streak would prefer to use "forename" if my brain manages to engage quickly enough to overtake my mouth. "First name" is how it's increasingly used on official forms, however, such as Government documents - I just checked my self-assessment return, and it's clearly labelled First Name/Middle Name/Last Name.

As for "Yank" - yeah, that'll work, though you can also use 'merkin or left-ponder if you want to confuse people :)