Yet another instance of hackerdom's peculiar attraction to mystical references -- a common humorous way of making exclusive statements about a class of things. The template is from the "Tao te Ching": "The Tao which can be spoken of is not the true Tao." The implication is often that the X is a mystery accessible only to the enlightened. See the trampoline entry for an example, and compare has the X nature .
THE X THAT CAN BE Y IS NOT THE TRUE X
Meaning of THE X THAT CAN BE Y IS NOT THE TRUE X in English
Jargon File English vocabulary. Английский словарь жаргона. 2012