A way of writing the
operating system name "Unix" that avoided the (TM) postfix
that was believed to be a legal requirement in the days when
Unix was a trademark of AT&T.
It has been suggested that there may be a psychological
connection to practice in certain religions (especially
Judaism) in which the name of the deity is never written out
in full, e.g. "YHWH" or "G--d" is used.
See also glob.