The concepts "old" or "young" have no real meaning when applied to periods before human language. We can talk about the Earth as "billions of years old" (and the concept may even be helpful in furthering our understanding of the Earth), but this has as little meaning as "the square root of minus 1" (which still has its uses in mathematics) or as "a unicorn's horn" (which has its mythological uses). The existence of a word for a thing - even for a useful thing - is no proof for the existence of that same thing.

The Earth therefore cannot be "older" than the age of human language in which the concept "old" first appeared. "Old" or "young" mean nothing without a human to express them. Nor do the words "God", "Earth" or any other word.

So phrases such as OLD or YOUNG EARTH only start to mean something when human speech first appears. The words that allow us to speak of the Earth and its age mark the beginning:

John 1:1 In the beginning was the WORD.

The Earth is therefore YOUNG, probably no older than the last Ice Age, since human speech began round about that time