This happened today before breakfast.
The explanation is that he had read “Tintin in the Congo” the night before.
Where Snowy (the dog) gets into a fight with a parrot… Pirates=>Parrot=>Psittacosis. It seems obvious now. (Still had to google it.)
NB: I am NOT under the impression or have the expectation that my son with Asperger’s is “a little professor” or whatever. His conception, memorizing and use of language is different than mine. I think that’s fascinating and it certainly keeps my own brain fit to keep up with him.