Caspian sits next to 4 phonetic neighbors — Casper, Cassian, and Cassius are the closest matches by sound. Most share Caspian's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"of the Caspian Sea"
"slender"
"good, blessing"
"handsome, cheerful"
"raven"
"of the ancient Roman Cassia gens"
"brook, small stream"
"God has given"
"wagon maker, cart driver"
"protector of mankind"
"hollow, ravine"
"great chief, eminent lord"
"rocky land, stony ground"
"born on Sunday"
"battle, warrior spirit"
"dark-complexioned"
"son of Brice"
"famous warrior"
"throne, master"
"great town"
Similar sound: These names share phonetic patterns with Caspian — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Latin/Geographic origins, giving them the same cultural heritage as Caspian.
Rhythm: Caspian is a 3-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.