Llewyn sits next to 3 phonetic neighbors — Llewelyn, Ewan, and Owen are the closest matches by sound. Most share Llewyn's Welsh cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"lion-like, resembling a lion"
"settlement of free men"
"wolf power, strong guardian"
"son of Piers (Peter)"
"sun ray, luminous"
"sad, sorrowful"
"helping stone, memorial stone"
"steep rock face by a crossing"
"elm tree"
"crooked, winding"
"mind, heart, spirit"
"divine peace (God + peace)"
"hill, headland, enclosure"
"rescuer, redeemer"
"great tide, sea flow"
Similar sound: These names share phonetic patterns with Llewyn — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Welsh origins, giving them the same cultural heritage as Llewyn.
Rhythm: Llewyn is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.