This would be an interesting point if Language stayed still and definitions did not change. The term Person, in its modern usage, has no religious meaning at all.

"Modern usage"???
Seriously? You consider 50 years ago ancient history or something?
The term "person" is a religious term. The fact that atheists are trying to culturally appropriate the word is suddenly ok, simply because you need to steal the term in order to make an absolutely false point, right?

"Person" has a theological meaning, always has, always will.
The UN Declaration on Human Rights uses the term in its theological context. The three Persons of the Trinity are distinguished only by the relationships (begetting, begotten, spiration, spirated). Made in the image and likeness of God, human persons are likewise distinguished by their relationships.

The whole UN document drips with Catholic theology explaining how this applies in the political realm. Not a surprise, since Jacques Mauritain, one of the principle advisors, was a devout Catholic. The modern political international world is built around the UN. So, yeah, "person" remains an intensely religious term, even if the people who throw it around are too ignorant of religion to realize what they are attempting to culturally appropriate.