shutdown appeared as a standalone utility in 4.1BSD.

http://mail-index.netbsd.org/source-changes-d/2016/09/13/msg008686.html
http://mail-index.netbsd.org/source-changes-d/2016/09/14/msg008691.html
PR:		212552
Approved by:	bcr (mentor)
Obtained from:	NetBSD
MFC after:	4 days
Differential Revision:	https://reviews.freebsd.org/D8105

sbin/shutdown/shutdown.8

@@ -28,7 +28,7 @@
 .\"     @(#)shutdown.8	8.2 (Berkeley) 4/27/95
 .\" $FreeBSD$
 .\"
-.Dd December 15, 2014
+.Dd September 21, 2016
 .Dt SHUTDOWN 8
 .Os
 .Sh NAME
@@ -215,7 +215,9 @@ a colon (``:'') for backward compatibility.
 .Xr init 8 ,
 .Xr reboot 8
 .Sh HISTORY
-The
+A
 .Nm
-utility appeared in
-.Bx 4.0 .
+command was originally written by Ian Johnstone for UNSW's modified
+.At "6th Edn" .
+It was modified and then incorporated in
+.Bx 4.1 .