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.