Eirian sits next to 5 phonetic neighbors — Arian, Kieran, and Orion are the closest matches by sound. Most share Eirian's Welsh cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"silver, bright, shining"
"immortal"
"land of the Scots"
"fair, blessed"
"from the southern lands"
"little poet"
"God is gracious"
"large homestead, big village"
"red-haired king"
"invented name (no traditional meaning)"
"archer, warrior of the yew"
"bold king, royal ruler"
"revered king"
"enthusiasm, ardor, passion"
"raven"
"wolf counsel (from Ralph)"
Similar sound: These names share phonetic patterns with Eirian — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Welsh arian (silver) origins, giving them the same cultural heritage as Eirian.
Rhythm: Eirian is a 3-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.