Cosmo sits next to 4 phonetic neighbors — Cosimo, Cosmos, and Roscoe are the closest matches by sound. Most share Cosmo's Italian-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"order, universe"
"son of the earth"
"place of elms"
"bright, clear, famous"
"farmer, earth-worker"
"lion"
"handsome, radiant one"
"wise protector from the valley"
"uncertain, possibly warrior spirit"
"marshy land by a lake"
"life's path, quest"
"dear, beloved"
"narrow land, island"
"staff bearer, wand wielder"
"qualitative time, the fullness of time"
"gift"
"from the River Irvine"
"rhythm, beat, flow"
"strong like a boar"
"flower (disputed folk etymology)"
"protector of mankind"
Similar sound: These names share phonetic patterns with Cosmo — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Greek origins, giving them the same cultural heritage as Cosmo.
Rhythm: Cosmo is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.