VMS Help POSIX Threads, PTHREAD routines, pthread_attr_setname_np, Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    This routine changes the object name attribute in the thread
    attributes object specified by the attr argument to the value
    specified by the name argument. A new thread created using the
    thread attributes object is initialized with the object name that
    was set in that attributes object.

    The object name is a C language string and provides an identifier
    that is meaningful to a person debugging a multithreaded
    application. The maximum number of characters in the object name
    is 31.

    This routine contrasts with pthread_setname_np(), which changes
    the object name in the thread object for an existing thread.