"...eventually Mad Baggins, who used to vanish with a bang and a flash and reappear with bags of jewels and gold, became a favourite character of legend..."
The Fellowship of the Ring, The Shadow of the Past

'Mad Baggins' started out as a name for Bilbo, after word of his adventures with Dwarves, Elves and Wizards started to spread through the Shire. Its use increased after Bilbo 'disappeared' at his 111th birthday party. But eventually, as the tales were exaggerated and told repeatedly over the years, 'Mad Baggins' became a creature of fairytales.