Comment by nkrisc

It doesn’t work because that’s just wrong. The semantic meaning of “king” is much more than simply “royalty” and “male”. And it will be different for different people based on their experiences and familiarity with English and world history as well.

Then there’s the phonetic angle in addition to the semantic one. Why isn’t cash emperor? Because “cash is king” is alliterative.

Then there’s the orthographic angle: it’s a lot easier to write “king” than “emperor”.