Today we mark the anniversary of the passing of James Parkinson on December 21, 1824. The Parkinson we honor today was not the satiric historian credited with observing that "the number of subordinate’s increases at a fixed rate regardless of the amount of work produced." Nor is he the fellow who believed that "work expands so as to fill the time available for its completion." Both those remarks came from Cyril Northolt Parkinson, a British author who died in 1993.

Who was James Parkinson? He was the British physician who first described the symptoms of the illness that came to be called Parkinson's disease. Parkinson's disease (also known as Parkinson's syndrome or Parkinsonism) is a chronic, progressive nervous disease that leaves muscles weakened and trembling. The tremor and weakness associated with Parkinson's inspired two earlier names for the neurological disorder: the English shaking palsy and its Latin translation, paralysis agates.

Although we now associate palsy with uncontrollable shaking, the word palsy is an offshoot of the word paralysis. But in this case the meaning of palsy has not shifted far from its historical sense; the linguistic ancestors of paralysis originally meant "to loosen" or "to disable."