Yes, the word Prototokos can - in certain contexts - mean 'firstborn'. But the word 'born' is not present in the word. And that is significant. The root of tokos being tikto then, of course, the concept of 'bringing forth' is present but not exclusively in regard to childbirth. The concept is broader and that is why tokos is used (by no less then the Holy Spirit) to describe a financial situation.
It is the first indication that an investment will be successful. It is the first tokenfruit of an investment that will, eventually, result in the multiplication of what was invested.
Out of it all comes the First TokenIndication that the purpose of Creation (from before the foundation of the world) will be a sound investment, a fruitful project.