A dictionary of Confusable Phrases: More Than 10,000 Idioms and Collocations

Note: 
The expression does not correlate in meaning with the
phrase King Charles—short for “King Charles’s Spaniel”: A little
“King Charles,” with a crimson ribbon round his neck is
jumping on the sofa.
King’s head —representation of a king on a postage stamp,
etc.: Take care never to step on a coin or banknote or a postage
stamp with the king’s head on it.
Note: 
The expression does not correlate in meaning with the
compound kinghead— a coarse annual plant (Ambrosia trifida):
The seeds consist of one central beak surrounded by a circle
of five or more marginal points, giving a king’s crown appear-
ance, hence the plant’s common names — kinghead and
crown-weed.
king for a day • king of day, the
king for a day —a person whose fame, popularity, etc., is
but short-lived: Superintendent Michael Snow was king for a
day in Middlefield this summer, serving as grand marshal of
the town’s bicentennial parade.
king of day, the —(poetic) the Sun: I have never seen Italy’s
far-famed sky, but I do not think it could surpass that evening
sunset. The king of day sinking into the bosom of Silver
Lake…
king of metals • queen’s metal
king of metals —gold: This king of metals will remain with
us as long as beauty wishes to adorn itself and designers wish
to create timeless classics in jewelry.
queen’s metal —an alloy of tin, antimony, lead and bismuth:
Queen’s metal serves also for teapots and other domestic uten-
sils.
king of waters • water king
king of waters— the name given to the river Amazon: There
are many large rivers … but what are these, severally, to the
“king of waters” on whose deep current fleets and navies may
float.
Note: 
The expression does not correlate in meaning with the
phrase king of the sea—
1
. a fabulous being that lives in water
and rules over the sea: The tale centers around the water spirit
Undine, daughter of the King of the Sea. 2. ruler of the sea:
There was Will Merrymouth, whose daring in fight and skill in
seamanship had won him the soubriquet of “King of the Sea.”
– 207 –
king of waters

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water king — = king of the sea 
1
: Lord Zeus holds the starry
hall on Olympus; he has given the briny sea to his brother
[Poseidon] the water king.