What was meant by non-God (or unambiguous)? Why did Stan Rogers and computermacgyver write a series of pseudonyms for “agnostics”? It comes from the word a (without) and the Greek “gnosis” (knowledge, specifically of sacredness). Contrast “atheist”, meaning, loosely, “one who is without God” (some wags even define an agnostic as “a chickens**t atheist”).

It was then co-opted by computer engineers into “platform-agnostic”, not knowing anything about the underlying system (thanks, Stan). In the process it morphed from a noun to an adjective but it at least retained the implication of lack of knowledge. From there it’s been applied more broadly (and, in my view, incorrectly).