I don't mean to rain on your parade, but the word "moot" as it is commonly used, is being used correctly. It does indeed come from judicial language, but not as you described above. I'm not saying that your definition of moot courts is incorrect, just that you are mistaken about where the term comes from as it is used in every-day speach.
Mootness refers to a specific aspect of justiciability. For judges to hear a case it must be justiciable, and there are many factors that affect justiciability. For example a case must be "ripe" before it can be heard. When Clinton was given the power of line-item veto six senators immediately sued, contending that it was unconstitutional (Raines v. Byrd). The case was dismissed outright because, since Clinton had yet to actually USE the line item veto the case was not yet "ripe" (also, since none of the senators had been injured yet none of them had "standing", another aspect of justiciability). As soon as Clinton used the line-item veto for the first time, however, the same court heard the case (Clinton v. City of New York) and ruled the practice unconstitutional.
"Moot" is, in a way, the opposite of "ripe". A good example, though I forget the name of the case, was a white student who filed suit against a law school in Washington for reverse discrimination after he was not admitted while less qualified minority students, he alleged, were admitted based on affirmative action. The law school allowed him to attend until the case was decided in court. But when the case finally made its way through the legal system the student was in his last semester of law school and the school indicated that they would give him his degree when he finished, regardless of the outcome of the lawsuit. So the case was dismissed as moot. If the controversy has evaporated, or one of the parties dies, or something to that effect, a court will rule the case moot and dismiss it.
On a side note, a little-known but significant impact of Roe v. Wade was that the justices created an exception to mootness. For years mootness had been used to keep anti-abortion laws from being examined by courts. A woman could not challenge anti-abortion laws before she was pregnant because, since the law wasn't directly harming her (because a non-pregnant woman cannot get an abortion even if it IS legal), she had no standing. But after she was pregnant the case couldn't work its way through the court because, by the time it was ever heard she had already delivered the baby, so the case was moot. Many pregnant women sued to have abortion laws struck down only to have their cases dismissed as moot before Roe v. Wade came along. The woman who successfully sued in Roe v. Wade (those are pseudonyms - real names are protected) had given birth and given the baby up for adoption four years before the case was heard before the Supreme Court. But the court ruled that mootness and non-justiciability cannot apply to a case where the very nature of the issue will make it impossible for courts to ever consider it.
...and so on.
edit: it occurs to me that I have suggested that the term is being used correctly, but, in fact, I'd guess that at least half the time someone uses the term they say, "...mute point." That's always irritating.