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. 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.