Well, of course all of us have been nonverbal at some point of our lives
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Well, I started speaking at about age one, but through to age 3 used echolalia, and my speech has always been atypical and, hmm, not coming so easy to me as most people, requiring more energy.
When I was young, about 4 or 5, I learned a lot of sign language and supplemented my speech with this (interesting that, without understanding or knowing that I was autistic or had difficulty with speech, that I sought out a means to augment my communication). At this time though, and through especially to about age 10, I would frequently go into strings of sound like gibberish, called it "my own language".
My most recent specific memory of doing this was when we were in the car going back home and I'd just got this big book called Natural Earth Living Earth and an astronomy-themed bookmark from Borders, and we were in the car going home and it was about 8 o'clock p.m. and all the street lights and everything were too bright and I went into strings of speech-like sounds. I did stuff like that when I was a toddler too, but also later when I would be stressed or couldn't find words or whatever.
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"There are things you need not know of, though you live and die in vain,
There are souls more sick of pleasure than you are sick of pain"
--G. K. Chesterton, The Aristocrat