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"
"fortune's keeper"
"God is with us"
"helper, one who helps"
"young lion"
"new house"
"God among us, divine presence"
"God is salvation, YHWH saves"
"pilgrim to Rome; from Rome"
"of the Sergii clan"
"drawn out of the water"
"from Lucania"
"of Mars, dedicated to Mars"
"of the gens Lucia (light)"
"divine strength"
"little one"
"gracious, dear, beloved"
"man, human being"
"protector of people"
"steadfast, firm"
"imperial title, ruler"
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.