The name Llywelyn is a boy's name of Welsh origin. Llywelyn and discussed in our forums with posts like "Picky Parents".
From the experts:
This is the original form of the ancient name also spelled Llewelyn. In ancient Wales, it was borne by two princes who for a time united their countrymen in North Wales and led opposition to the power of the Norman barons in the south. Llywelyn ap Iorwerth was the greatest of the Welsh rulers of the Middle Ages. This is a popular patriotic name, with nicknames Llelo and Llew, which is also Welsh for 'lion.'