Marvin sits next to 3 phonetic neighbors — Melvin, Kevin, and Mervin are the closest matches by sound. Most share Marvin's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"sea fortress, sea friend"
"God the highest (variant interpretation)"
"deliverance of God"
"fallow land, uncultivated land"
"son of John (via Jack)"
"gift, from the sea"
"cool breeze over the mountains"
"illustrious through nobility"
"handsome, cheerful"
"heart, soul"
"modern elaboration of Jason"
"variant of Carson"
"son of Otto"
"narrow strait"
"brave warrior (later folk etymology)"
"battle cry"
"the king"
"God has given"
"divinely appointed, called by God"
"rock, harmony"
"wise counselor"
Similar sound: These names share phonetic patterns with Marvin — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old Welsh Mervyn origins, giving them the same cultural heritage as Marvin.
Rhythm: Marvin is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.