Errol Dunkley- OK FRED Yagga Yagga Explanation

One question I've always wanted to ask Errol Dunkley, since the first time i heard OK Fred many years ago. Finally got to ask him while he was voicing dubplates at the Friendly Fire Studio.. What is a yagga yagga? Check the website for upcoming dub sessions.. www.friendlyfiremusic.com