Wernicke's aphasia lets you speak fluently while making no sense

In 1874, neurologist Carl Wernicke described stroke patients who spoke in smooth, grammatical sentences that carried almost no meaning — fluent jargon. Unlike Broca's patients, they often couldn't tell their own speech was broken, and their comprehension of others' words failed too. The finding pinned a second, distinct language center to the brain's temporal lobe.

— Carl Wernicke, Der aphasische Symptomencomplex — 1874 monograph