The name Llewellyn is a boy's name of Welsh origin meaning "leader's image". Llewellyn and is often added to lists like Geek Chic Names for Boys and discussed in our forums with posts like "Picky Parents - Sibsets Version".
From the experts:
Llewellyn/Llywelyn is a common patriotic first name in Wales, with its distinctive Welsh double LL's; in the U.S. Llewellyn would make a daring choice, though with the chance that some might find the ellen sound slightly feminine.
Two princes who played a great role in the medieval Welsh quest for independence were Llewelyn Fawr (Llewelyn the Great) and Llywelyn yr Olaf (Llywelyn the Last).
Llewelyn Moss is a major character in Cormac McCarthy's No Country for Old Men, played on screen by Josh Brolin.
Llewellyn, which can be spelled in a number of ways, has some appealing, if quirky, short forms as well--Llew, Lleu and Llelo.