Long long ago a ghariyal lived in the Poorna river near Kalladi village in Keralam. One time a young boy came for a bath in the river and the ghariyal grabbed his foot. In the struggle that followed the boy ( miraculously for him ) got away. However, a small piece of the boy's toe nail from the smallest toe of the boy's left leg broke off and the ghariyal accidentally swallowed it.
Since that day the ghariyal never forgets the incident in any of his re-incarnation, also it never forgets to grab the feet of that boy.
I am that ghariyal, the boy was Adi Sankaracharya.