'You see,' he went on after a pause, 'it's as well to be provided for EVERYTHING. That's the reason the horse has all those anklets round his feet.'
'But what are they for?' Alice asked in a tone of great curiosity.
'To guard against the bites of sharks,' the Knight replied. 'It's an invention of my own.'

Through the Looking Glass (And What Alice Found There), Chapter 8 - "It's my own Invention"