My misunderstanding.
emacs-24.3.92 -Q -l eieio
C-h f object-set-name-string
object-set-name-string is an alias for `eieio-object-set-name-string'
in `eieio.el'.
(object-set-name-string OBJ NAME)
This function is obsolete since 24.4;
use `eieio-object-set-name-string' instead.