vfork() first appeared in 3BSD which pre-dates 2.9BSD. Verified via the

copy of 3BSD on disc 1 of "The CSRG Archives".

PR:		198612
MFC after:	1 week

lib/libc/sys/vfork.2

@@ -28,7 +28,7 @@
 .\"     @(#)vfork.2	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd November 13, 2009
+.Dd April 6, 2015
 .Dt VFORK 2
 .Os
 .Sh NAME
@@ -111,7 +111,7 @@ Same as for
 The
 .Fn vfork
 system call appeared in
-.Bx 2.9 .
+.Bx 3 .
 .Sh BUGS
 To avoid a possible deadlock situation,
 processes that are children in the middle