Username checks out.

Oh, jesus christ. 98% of the time, "hydrophobia" does not refer to fear of water.

Perhaps true. What would you call somebody who was afraid of water, though?

You cannot divine the meaning of a word you've never seen before by breaking it down into sub-word units of meaning.

You absolutely can for many, many words.

Not all words, of course. And some words, like hydrophobic, gain additional meanings over time.

you cannot definitively know what a word means

Sure, but this is a new standard that you seem have come up with in your rage.