/etc/rc was earlier than 4BSD.  The first mention I can find in the
manuals on TUHS is in the fourth edition manual's init page.

The rc history section appeared in csrg sccs rev 6.2 (1991) when the
file was converted to mdoc.

Index: share/man/man8/rc.8
===================================================================
RCS file: /cvs/src/share/man/man8/rc.8,v
diff -u -p -r1.46 rc.8
--- share/man/man8/rc.8	10 Feb 2020 13:18:20 -0000	1.46
+++ share/man/man8/rc.8	30 Jun 2024 03:06:31 -0000
@@ -212,4 +212,4 @@ at boot time.
 The
 .Nm
 command appeared in
-.Bx 4.0 .
+.At v4 .