WordPress at a glance
function is not described

wp_get_original_referer() WP 2.0.4

Retrieve original referer that was posted, if it exists.

No Hooks.

Return

String/false. False if no original referer or original referer if set.

Usage

wp_get_original_referer();

Code of wp get original referer: wp-includes/functions.php WP 5.2.2

<?php
function wp_get_original_referer() {
	if ( ! empty( $_REQUEST['_wp_original_http_referer'] ) && function_exists( 'wp_validate_redirect' ) ) {
		return wp_validate_redirect( wp_unslash( $_REQUEST['_wp_original_http_referer'] ), false );
	}
	return false;
}