Yaga yaga

Having just heard it on the radio this morning, I now have "OK Fred, now you're a yaga yaga" (Errol Dunkley) on the brain. But what on earth is a yaga yaga? Google is most uninformative.
  • Current Mood: curious curious
  • Current Music: "OK Fred, now you're a yaga yaga" in my head
I always heard it as 'yukka yukka'. Not that that makes it any clearer. And now I have it as an earworm too. :-)
I actually heard it as "yugga yugga" but Google assures me it is "yaga yaga". Sadly, though, Google is silent on the issue of what "yaga yaga" might mean.