private function getGatewayFieldName($defaultName, $gateway = null)
    {
        if (!$gateway) {
            if (!$this->gateway) {
                return false;
            }

            return $this->getGatewayFieldName($defaultName, $this->gateway);
        }

        $renameMap = $this->config()->rename;

        if (is_array($renameMap) && array_key_exists($gateway, $renameMap)) {
            $gatewayMap = $renameMap[ $gateway ];
            if (array_key_exists($defaultName, $gatewayMap)) {
                return $gatewayMap[ $defaultName ];
            }
        }

        return false;
    }