"The adjective moot is originally a legal term going back to the mid-16th century. It derives from the noun moot, in its sense of a hypothetical case argued as an exercise by law students. Consequently, a moot question is one that is arguable or open to debate.
But in the mid-19th century people also began to look at the hypothetical side of moot as its essential meaning, and they started to use the word to mean "of no significance or relevance." Thus, a moot point, however debatable, is one that has no practical value. A number of critics have objected to this use, but 59 percent of the Usage Panel accepts it in the sentence The nominee himself chastised the White House for failing to do more to support him, but his concerns became moot when a number of Republicans announced that they, too, would oppose the nomination.
When using moot one should be sure that the context makes clear which sense is meant." (AHD)(AHD)
