U++

class Thread {
   // Probably some kind of synchronization is need.
   void   SetName(const String& name) { this->name = name; }
   String GetName() const             { return name; }

   // On starting thread we should use platform depend code that set thread name on system side.
}

POSIX documentation for set name thread function: http://man7.org/linux/man-pages/man3/pthread_setname_np.3.html

How to display thread with names (for example firefox on POSIX):
ps H -C firefox -o 'pid tid cmd comm'