"Taffy was a welshman
Taffy was a thief
Taffy came to our house
And stole a leg of beef..."

The nursery rhyme is derived from the Normans who invaded Wales, drove the Welsh back to the hills and occupied the fertile land. The Welsh resisted and formed raiding parties, carrying off the Normans' cattle and food to the safety and protection of the hills. One notable raider was Ifor Bach, who who lived above Caerffili and staged successful raids on the land around Cardiff. So now you know!