Right, different origins, both Greek.
The planet comes from the Greek/Roman god of the underworld, while the other comes from the Greek word for "wealth".
See the Etymology sections here:
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Plu·to

Function:
noun
Etymology:Latin
Pluton-, Pluto, from Greek
Plout
n
Date:14th century
1 : the Greek god of the underworld -- compare
DIS
2 [New Latin]
: the planet with the farthest mean distance from the sun -- see
PLANET table
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plu·toc·ra·cy
Etymology:Greek
ploutokratia, from
ploutos wealth +
-kratia -cracy
1 : government by the wealthy
: the rule or dominion of wealth or of the rich
2 : a controlling or influential class of rich men
: a body of
plutocrats
http://unabridged.merriam-webster.com
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