Cassian sits next to 4 phonetic neighbors — Sebastian, Florian, and Cyprian are the closest matches by sound. Most share Cassian's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"of the Cassian family (Roman gens)"
"river that swallows all rivers"
"mountain goat, to ascend"
"declared innocent, acquitted"
"healer (if derived from Jason/Kason)"
"prosperous spearman"
"son of John (via Jack)"
"dweller by the woods"
"lion-like, brave"
"always king"
"little cloak, beloved"
"crooked nose"
"priceless one"
"God has heard (via Jaden influence)"
"from the island of Rhodes"
"western enclosure"
"joy, happiness"
"wayfarer, traveler"
"drawn out of water"
"holy, sacred place"
"invented modern combination name"
Similar sound: These names share phonetic patterns with Cassian — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Latin origins, giving them the same cultural heritage as Cassian.
Rhythm: Cassian is a 3-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.