Quincy sits next to 3 phonetic neighbors — Quinton, Quentin, and Percy are the closest matches by sound. Most share Quincy's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"estate of the fifth son"
"invented name, no established etymology"
"ardor, enthusiasm, fierceness"
"lawful, true to one's pledges"
"power, strength, ruler"
"battle, warrior spirit"
"arrow maker"
"gatekeeper, doorman"
"shelter, shield"
"divine peace"
"renowned in battle"
"laughter"
"stone worker (via Mason)"
"sea, ocean (kai component)"
"from Lucania"
"to heal (from iasthai)"
"cloud"
"son of"
"fair-haired one"
"chief desire"
"wise protector"
Similar sound: These names share phonetic patterns with Quincy — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have French/Norman origins, giving them the same cultural heritage as Quincy.
Rhythm: Quincy is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.