Scientifically, a PASTERN is the part of the horse's foot between the fetlock and the top of the hoof. In his influential Dictionary of the English Language, Samuel Johnson famously misdefined the word as "the knee of the horse." When a woman asked Dr. J to explain why he had botched the definition, he replied, "Ignorance, Madam. Pure ignorance."
"The Protean Pastern,"
Word Ways: Vol. 45
, Article 8.
Available at: http://digitalcommons.butler.edu/wordways/vol45/iss4/8