which means "those who know"

The word 'agnostic' came about by adding the negative prefix "a-" to the name of the ancient Gnostics (meaning "those who know") who sought salvation through occultism.*

Thomas Henry Huxley used the word in an article in 1889. a logical way to conclude the founding of a new noun.

George Jacob Holyoake, an English reformer (1817 -1906) also claims to have coined the word. He lectured with the premise "I do not believe there is such a thing as a God." He was sentenced to six months in prison for another speech against the supernatural existence of God.

Without the baggage of religion both Huxley and Holyoake could have reasoned the logical use of the negative "a-" and used the same word independently. Ideas need not have a specific beginning as the Christian world would have us believe in absolute black and white with no exceptions.

* from 2000 YEARS OF DISBELIEF, by James A. Haught
Prometheus Books, Amherst NY, 1996