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 BNG".
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.