Bumpkin
From Tolkien Gateway
Bumpkin was a pony belonging to Meriadoc Brandybuck, and was one of five ponies that Merry had ready for the Hobbits journey at Crickhollow.
At the home of Tom Bombadil, the ponies became friends of Fatty Lumpkin, a pony of Tom's. And when they became frightened in the Barrow-downs and ran off to find Fatty. So Tom called them all back with the names he had given them Bumpkin, Wise-nose, Swish-tail, and White-socks. Eventually they all returned with all the bagge, and went back on their journey with the Hobbits.
During their stay at the Prancing Pony the Hobbit's ponies were let out to delay the them from leaving Bree. And of course the ponies ran into the Downs to find Fatty. Where they stayed with Tom for a while, till news came about what happened at Bree. So he sent the Ponies back to Barliman Butterbur landlord of the Prancing Pony, and they stayed there working for Barliman, they were taken well cared for by Bob.
