Index: src/wp-includes/media.php
===================================================================
--- src/wp-includes/media.php	(revision 40278)
+++ src/wp-includes/media.php	(working copy)
@@ -3434,8 +3434,8 @@
 		'unattached'             => __( 'Unattached' ),
 		'trash'                  => _x( 'Trash', 'noun' ),
 		'uploadedToThisPost'     => $post_type_object->labels->uploaded_to_this_item,
-		'warnDelete'             => __( "You are about to permanently delete this item.\n  'Cancel' to stop, 'OK' to delete." ),
-		'warnBulkDelete'         => __( "You are about to permanently delete these items.\n  'Cancel' to stop, 'OK' to delete." ),
+		'warnDelete'             => __( "You are about to permanently delete this item.\nThis will remove it from your site.\n  'Cancel' to stop, 'OK' to delete." ),
+		'warnBulkDelete'         => __( "You are about to permanently delete these items.\nThis will remove them from your site.\n 'Cancel' to stop, 'OK' to delete." ),
 		'warnBulkTrash'          => __( "You are about to trash these items.\n  'Cancel' to stop, 'OK' to delete." ),
 		'bulkSelect'             => __( 'Bulk Select' ),
 		'cancelSelection'        => __( 'Cancel Selection' ),
Index: src/wp-includes/script-loader.php
===================================================================
--- src/wp-includes/script-loader.php	(revision 40278)
+++ src/wp-includes/script-loader.php	(working copy)
@@ -77,7 +77,7 @@
 
 	$scripts->add( 'common', "/wp-admin/js/common$suffix.js", array('jquery', 'hoverIntent', 'utils'), false, 1 );
 	did_action( 'init' ) && $scripts->localize( 'common', 'commonL10n', array(
-		'warnDelete'   => __( "You are about to permanently delete these items.\n  'Cancel' to stop, 'OK' to delete." ),
+		'warnDelete'   => __( "You are about to permanently delete these items.\nThis will remove them from your site.\n 'Cancel' to stop, 'OK' to delete." ),
 		'dismiss'      => __( 'Dismiss this notice.' ),
 		'collapseMenu' => __( 'Collapse Main menu' ),
 		'expandMenu'   => __( 'Expand Main menu' ),