The Collaborative International Dictionary of English v.0.48:

Nana \Na"na\, n. [prob. from babytalk.]
   Grandmother.
   [PJC]

The Jargon File (version 4.4.7, 29 Dec 2003):

NANA
 //

    [Usenet] The newsgroups news.admin.net-abuse.*, devoted to fighting spam
    and network abuse. Each individual newsgroup is often referred to by adding
    a letter to NANA. For example, NANAU would refer to
    news.admin.net-abuse.usenet.

    When spam began to be a serious problem around 1995, and a loose network of
    anti-spammers formed to combat it, spammers immediately accused them of
    being the backbone cabal, or the Cabal reborn. Though this was not true,
    spam-fighters ironically accepted the label and the tag line ?There is No
    Cabal? reappeared (later, and now commonly, abbreviated to ?TINC?).
    Nowadays ?the Cabal? is generally understood to refer to the NANA regulars.