protected String getUsernameParameterFromRequest(final HttpServletRequest request) {
        val throttle = getConfigurationContext().getCasProperties().getAuthn().getThrottle().getCore();
        return request.getParameter(StringUtils.defaultIfBlank(throttle.getUsernameParameter(), "username"));
    }
Throttled login attempt action code used to tag the attempt in audit records.
support/cas-server-support-throttle-core/src/main/java/org/apereo/cas/throttle/AbstractThrottledSubmissionHandlerInterceptorAdapter.java