gibber /jibbr/ • v. speak rapidly and unintelligibly, typically through fear or shock. n. such speech or sound.
gibberish /jibbrish/ • n. unintelligible or meaningless speech or writing; nonsense.
My son Sweeney is walking around the house talking to himself and anything or anyone who will listen. He speaks a most incredibly fluent gibberish. I'm astonished at the sheer variety of sounds coming out of his mouth.
I've tried to imitate him but it's the aural equivalent of an adult trying to draw like a child: close, but somehow missing that special something that makes the original so fascinating.
This morning we speculated that he might have been speaking Russian all this time and we've never realised it.