Lewellyn is a unique and distinctive given name of Welsh origin, derived from the elements Llwyd meaning "gray" and Elfyn meaning "noble". It has been traditionally used as both a masculine and feminine name in Wales but has seen greater usage as a male name elsewhere. Lewellyn was popularized in English-speaking countries by its use in Sir Thomas Love Peacock's 1817 novel "The Misfortunes of Elphin", where it appeared as the given name of one of the main characters. Despite its Welsh roots, Lewellyn has also been associated with Cornish and Breton origins due to its shared elements with similar names like Llwyd andEloquent in these languages.
The name Lewellyn experienced a spike in popularity between 1917 and 1940, with the most notable increases occurring in the years 1933 (6 births) and 1940 (7 births). The total number of babies named Lewellyn during this period was 33.