mu

The idea of Mu first appeared in the works of the antiquarian Augustus Le Plongeon (1826¨C1908), a 19th century traveler and writer who conducted his own investigations of the Maya ruins in Yucatan. He announced that he had translated the ancient Mayan writings, which supposedly showed that the Maya of Yucatan were older than the later civilizations of Atlantis and Egypt, and additionally told the story of an even older continent of Mu, which had foundered in a similar fashion to Atlantis, with the survivors founding the Maya civilisation. (Later students of the Ancient Maya writings have found that Le Plongeon's "translations" were based on little more than his vivid imagination.)
Mu (Japanese), Wu/Mou (Chinese (Mandarin/Cantonese); is a word which can be roughly translated as "without" or "have not". While typically used as a prefix to imply the absence of something (e.g. musen for "wireless"), it is more famously used as a response to certain koans and other questions in Zen Buddhism, intending to indicate that the question itself was wrong.
The 'Mu' koan is as follows: A monk asked Zen master Zhaozhou, a Chinese Zen Master (in Japanese, J¨­sh¨±): "Has a dog Buddha-nature or not?", Zhaozhou answered: "Wu".
Some earlier Buddhist thinkers had maintained that creatures such as dogs did have the Buddha-nature; others, that they did not. Zhaozhou's answer has subsequently been used by generations of zen students as their initiation into the zen experience.
Since the expression 'wu' in Chinese is similar to the sound the Chinese use to imitate a dog's 'woof', an alternate 'explanation' of the utterance has been proposed suggesting that Zhaozhou was imitating a dog in reply, i.e. he answered the question by 'being' the dog. This is consistent with the general principle that Koan 'answers' usually involve adopting radical change of perspective, instead of a logical or linguistic 'answer'.
The Mirror Universe (MU) is a fictional parallel universe in which the plots of several Star Trek television episodes take place. The characters in the Mirror Universe are generally the same as the characters in "normal" Star Trek continuity (for example, it has a James T. Kirk and a Mr. Spock), but their personalities are, on the whole, much more aggressive, mistrustful, and opportunistic. Whereas the Star Trek Universe usually depicts an optimistic future which values peace and understanding, episodes set in the Mirror Universe show it to be marred by continual warfare, and compassion is seen as a liability.