Marco sits next to 4 phonetic neighbors — Marcus, Mario, and Mark are the closest matches by sound. Most share Marco's Italian-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"of Mars, warlike"
"breath, vapor, impermanence"
"behold, a son"
"from the city of Milan"
"God is salvation, Yahweh saves"
"of Mars, consecrated to the god of war"
"little one"
"powerful, brave king"
"helper, one who helps"
"defender of men"
"Frenchman"
"fortune's keeper"
"valiant, brave"
"army man, soldier"
"God hears"
"of the gens Lucia (light)"
"of the Sergii clan"
"brave and powerful"
"little saint"
"of Mars, dedicated to Mars"
"wealth, fortune, prosperity"
Similar sound: These names share phonetic patterns with Marco — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Latin origins, giving them the same cultural heritage as Marco.
Rhythm: Marco is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.