a funny word

zyc50

I saw the word \"misunderestimate\" in yahoo dictionary.
I've never actually heard of it before,
so I checked on Google and it appears it was coined by no other than
George W. Bush. I don't really understand how it got into the Yahoo
Dictionary, as strictly speaking it's not yet a valid word.
The reason I find it amusing is that usually when we add the prefix \"mis\"
to verbs, it denotes that the action is a mistake or somehow incorrect.
Therefore, \"verb\" and \"mis+verb\" are usually opposites (e.g. understand &
misunderstand). However, the verb to \"underestimate\" means \"making an
incorrect estimate that turns out to be too low\", so it already has the
element of mistake in its definition. To \"misunderestimate\" would mean \"to
incorrectly or mistakenly make an incorrect estimate that turns out to be
too low\", which is in fact the same thing. In other words, \"underestimate\"
and \"misunderestimate\" would mean the same thing, thus the purpose of
adding the prefix in the first place is lost.
For example, in your sentence: In the beginning of this (regular) season,
he was underestimated, undervalued. Now they know they have
\"misunderestimated\" him.
You wanted to convey that they wrongly underestimated him. However doesn't
\"Now they know they have underestimated him\" mean exactly the same thing?