A penny has dropped - I've realised that what I did as a child is what is discussed on this board under "echolalia" or "self-stimulation" or "repeating verbatim phrases".
At, say, age 7 or 8, Child A would say something to me. I would feel nervous. The pattern and pitch of what the child said would resonate really strongly, and so would some of the individual words, especially words that I liked or didn't like or had heard in some comedy programme on tv (like a student who is reminded by everthing they hear of some phrase in a Monty Python sketch).
In my head, it was all very logical. Child A would say "A!". I would think "hmm, A - yes, like B - and C! - EEE!". And I would reply "F!" - somewhat nervously.
To which Child A would say "You're strange" or "you're funny" and I would feel sad.
Good news though is that by the time I was a teenager doing English literature, it became a fantastic skill - you can "see" and "hear" all the echos in the phrases used in sentences within long novels - you can remember the echos both within the text and with other texts.
All quite creative really . Rather lonely at the time though! I never understood why they didn't understand, that was the pity of it.
But this is yet another example of how a behaviour is treated as evidence that the child doesn't want to communicate, whereas in fact the child may be doing their level best to respond - it's just that she has processed the message differently to the way other people do.
.