This is about the secret society. For the band, see The KLF.
The Justified Ancients of Mummu (The JAMs) are a secret society based on a primeval Babylonian deity, Mummu.
Simon Moon is a member.
The JAMs are a sort-of precursor to the Erisian Liberation Front (ELF) and the Legion of Dynamic Discord (LDD).
Cecil Rhodes (fictionally) coined the phrase, "Kick Out the JAMs" which later became the basis of the MC5 song... an apparent Illuminati plot to rub it in the JAMs' faces.
The authors associated Mummu with the the idea of primordial chaos in the novel.