Arcaius sits next to 3 phonetic neighbors — Arcadius, Lucius, and Cassius are the closest matches by sound. Most share Arcaius's Greek-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"from Arcadia, of the idyllic land"
"hay meadow"
"immortal, eternal"
"faithful, genuine, true"
"from Pacy-sur-Eure"
"grace, beauty"
"valley dweller"
"strong lord"
"place name: fortified settlement"
"twin (Thomas variant)"
"free man"
"anointed one"
"God's beauty (Jah + beauty)"
"joyful celebration, festivity"
"race, swift movement"
"slender, narrow"
"settlement by water"
"excellence, virtue"
"modern invented name, bold and distinctive"
"beloved (possibly influenced by love)"
Similar sound: These names share phonetic patterns with Arcaius — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Greek origins, giving them the same cultural heritage as Arcaius.
Rhythm: Arcaius is a 3-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.