> I have a set of multiple given names, each of them given by a godfather. In our tradition and law they are equal because treating one of them specially is insulting to the godfathers (which you caught me guilty of).

I don't see how changing "first" to "given" lessens the insult to those N - 1 godfathers.

And having "multiple first names" is not that rare.

> And having "multiple first names" is not that rare.

Example: https://www.service-public.fr/particuliers/vosdroits/F882?la...

Can you give your child several first names?

There is no rule on the number of first names of the child.

However, the registrar may consider that the multiplicity of first names is contrary to the best interests of the child.

FYI Any first name entered in the birth certificate can be selected as common first name, whatever his order.

All the given names are equal, none of them is first or middle.

All of them are first names.

Going by the Cambridge definition you linked above[1], indeed yes. I checked other reputable dictionaries and they are mostly similar.

But by these definitions a middle would also be a first name, which is confusing.

[1] the name that was given to you when you were born and that comes before your family name