static String rawHeaderName(AsciiString name) {
        final String headerName = inverseMap.get(name);
        if (headerName != null) {
            return headerName;
        } else {
            return name.toString();
        }
    }
Returned the raw header name used when creating the specified {@link AsciiString} with
{@link #create(String)}.
core/src/main/java/com/linecorp/armeria/common/HttpHeaderNames.java