The "names" option of ns_cache was added 4 years ago. When you install a recent version of ns_cache, "names" is a valid option. The error message above shows clearly that you have installed the old version.
See http://alice.wu-wien.ac.at:8000/xowiki-faq/#install-ns_cache
http://aolserver.cvs.sourceforge.net/aolserver/nscache/tclcache.c?view=log
