[PATCH] doc: explain why dd is called "dd"

[Paul Eggert]

I pushed this hoping that it may help forestall questions about
why dd is so, ahem, *unusual*....

* doc/coreutils.texi (dd invocation): Mention JCL.
---
 doc/coreutils.texi | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 7f8c0d1..70e7ca0 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -8045,7 +8045,9 @@ dd @var{option}
 @end example
 
 The only options are @option{--help} and @option{--version}.
-@xref{Common options}.  @command{dd} accepts the following operands.
+@xref{Common options}.  @command{dd} accepts the following operands,
+whose syntax was inspired by the DD (data definition) statement of
+OS/360 JCL.
 
 @table @samp
 
-- 
1.7.11.7