Monaco sits next to 3 phonetic neighbors — Monica, Mako, and Marco are the closest matches by sound. Most share Monaco's Italian-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"solitary monk, single house"
"sea, ocean"
"related to Samir: lively conversationalist"
"bear man, noble bear"
"God is salvation"
"to descend, he who descended"
"World ruler (from Donald prefix Don-)"
"born on Sunday (in some traditions)"
"black banded gemstone"
"desiring peace, will and peace"
"from the town of Dax"
"son of Cadán, little battle"
"possibly king/blessed (phonetic associations)"
"wheel maker, cartwright"
"modern American invented name"
"noble excellence, virtue"
"best, excellent"
"improvement, change for the better"
"prince, commander"
"Short form of Uilliam, the Irish form of William"
"saddlemaker, one from the homestead"
Similar sound: These names share phonetic patterns with Monaco — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Greek (Monoikos) origins, giving them the same cultural heritage as Monaco.
Rhythm: Monaco is a 3-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.