It's being going dumb! "Goin Dumb" is just a catch phrase, so everyone figured they'd call it that. Go stupid, go dumb, get retarded, do the dummy, act a fool, act an ass, actin bad, etc. That's just history evolving.
see from reading i see the question is when did the WHOLE bay start going dumb, not when did the bay start goin dumb, cuze the bay started goin dumb in 89 but you didn't see Billy, Nicole, Mary or Joseph from Rancho Solano poppin their collar in the 98 Camry with the thizz face. Now I think I noticed that everyone started to go stupid go dumb after Mac Dreezy put out Ronald Dreagan. Shit I live in Vacaville and I can't drive down the street without seein someone goin stupid in they car, and shit 2-3 years ago these kids didn't even know Mac Dre was and use to sit in their car with a straight face listenin to Nelly or Green Day or some shit, that shit picked up quick, makes you wonder how big he coulda got
MAC DRE mostly started that shit... but i give a fuck i say humpty hump shock g was going dumb in the late 80's he says that shit too..... digital underground never gets credit but thats a different story.......
Go dumb - IS the federation was the single after hypee. So Fed has some part in naming go dumb...mac dre said go stupid..Same thing pretty much dem nikka from the same place...
so i would say it came from vallejo