I think know what you are saying analaura.
My brother, God rest him, had brain surgery for a tumor and the surgery irreparably damaged his brain, resulting in a condition called aphasia, which caused him to speak nonsensically. He'd utter paraphasias, i.e., words that were not what he meant. He'd call a car a tree, or a dog an elephant...stuff like that. He knew what he WANTED to say but just couldn't get the right words out.