I see this as the most likely explanation
It is possible that Jerome’s difficulties with producing speech could be linked to a brain injury, most likely in Broca’s area, the part of the brain that regulates speech. Jerome would have been incapable of speaking in any sort of understandable language.[1] This may account for Jerome’s ability to make animalistic noises, but not replicate human language.
It also seems pretty likely that Jerome was “Gamby,” the known double-amputee from across the bay, as described at the end of the article
The identification depends on how correct Jerome’s rescuers were in thinking his amputations were not completely healed and so were recent. Gamby showed up across the bay four years previous and was missing his legs then.
Why not both ¯\_(ツ)_/¯
