I found that the term "aphasia" or aphasiac has been used multiple times in the reading (525,588, previously but am too lazy to find). Aphasias are fascinating neurological deficits. Two common ones, Broca's and Wernicke's, deal with language processing. With Wernicke's, for example, you talk nonsensically even if you might understand what people are saying to you. The words coming out of your mouth simply don't align with thoughts.

While I feel that DFW uses some interesting adjectives, the continued references to neurological conditions (Madame Psychosis' radio show scene filled with neuroanatomy, etc) struck me as very interesting.