Why do people assume 'agnosticism' and 'gnosticism' are related concepts?

So many people seem to misunderstand the meaning of term agnostic and gnostic... it has got to the point that the misunderstanding is literally changing the meaning...

Agnostic - A (without) + Gnosis (knowledge) - is a concept that refers typically to a position of the existence of deities... it means literally "i dint know"... Although i agree it does not necessitate exclusivity with atheism/theism, it can still exist on its own... that is, someone CAN be agnostic without also being atheist/theist.

Gnosticim - Gnosis (knowledge) - this term DOES NOT refer to the existence of deities, but rather gnosticism refers to the believe in INNER-KNOWLEDGE...

They both share the root word Gnosis but actually refer to COMPLETELY DIFFERENT concepts. So please people, stop saying that agnosticism and gnosticism are opposites... they are not.
No its not a rant... i specifically asked WHY people confuse concepts
they are not opposite... they may seem to be opposite because of their etymology but in the English language refer to different concepts
Teapotistic... No actually you misunderstand the terms... If someone makes NO judgment on the existence of deities they are agnostic without being atheistic/theistic... And gnosticism has no position relating to the existence of deities, it is a separate spiritual position...

and i do study philosophy... no point using appeals to authority
plus limiting positions to 4 possible outlook ignores other outlooks such as agnosticism and atheism. All in all there are five major positions which can often be combined to suite other outlooks... (atheism, theism, agnosticism, atheism, ignosticism)

Seems to me that you just answered your own question. Does that make your question a rant? I think it does.

I don't know for certain; however, I'm speculating that the two are mixed up simply due to their similar spellings. I'm sure it's an honest mistake or misunderstanding.

Perhaps for the same reason evangelicals insist that all atheists believe deep inside their brains, or that we suffered some horrible experience. Both assertions are false.

Thank you for making the distinction, but most of us knew this already. However, there's always a chance for someone to misunderstand.

well you can be a gnostic atheist
or an agnostic atheist

They don't necessarily think they are related concepts. They are just going into the etymological meaning of it.

Basically, they _ARE_ OPPOSITES...

"Gnosticism" is about "special knowledge," and agnosticism is the belief that you CANNOT KNOW anything about any god or gods.

Since one is all about knowledge and the other claims that there can be no such knowledge, how can you say they are not opposite? You accurately report the derivation of "agnosticism," but seem to fail in recognizing the significance of the Greek prefix "a-" and its negation of the premise.

"someone CAN be agnostic without also being atheist/theist".
You are wrong. You misunderstand the real meaning of agnosticism in Philosophy. Agnosticism is contextual, not limited to the context of "belief in deity". When the context is "belief in deity", NO, agnostics CANNOT be in its own.

Agnosticism and gnosticism are positions to question "Do you claim to know?"
Atheism and theism are positions to question "Do you believe in deity?"

When the above two questions are asked, there can be agnostic theists, agnostic atheists, gnostic theists, and gnostic atheists. When other questions are asked, i.e. "what kind of deity?" or "is the concept conceivable?", then there can also be deism, pantheism, pantheism, agnosticism, etc.

Study Philosophy, especially T.H. Huxley. You'll see what I am talking about.