bug#3001: 23.0.92; doc for regexp construct (?:

Emacs calls regexp groups that use the grouping construct "(?:" "shy
groups".  I don't get the impression that that is a common term for
this construct, outside Emacs.  Googling "shy group" shows only Emacs
hits.  Googling and searching for regexp groups shows that terms such
as "non-capturing group" and "unnumbered group" are more typically
used for "(?:".
 
And the Emacs doc for "(?:" even explains it as an unnumbered group.
It doesn't explain or hint at the meaning of "shy" at all.  This seems
like a poor choice of words.
 
"Shy" might already have become the Emacs "traditional" terminology,
so that it can't easily be replaced (some people will look for it).
But at least some explanation of the use of the word "shy" is in
order, if only for mnemonic purposes.  What were you thinking? ;-)
(Perhaps it is translated from some other language, where it has more
than one meaning?)
 
More importantly, this construct does not appear to be indexed in the
manual.  It should be indexed under "(: in regexp", as well as under
"regexp non-capturing group" and "regexp unnumbered group" - and of
course "regexp shy group", if that term is kept.
 
 
 
In GNU Emacs 23.0.92.1 (i386-mingw-nt5.1.2600)
 of 2009-03-30 on SOFT-MJASON
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4)'