Cooper sits next to 3 phonetic neighbors — Hooper, Crooper, and Couper are the closest matches by sound. Most share Cooper's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"From the Middle English 'couper' or Middle Low German 'kuper'; an occupational surname for a barrel maker"
"resolute protector, strong-willed guardian"
"mild, peaceful"
"God is gracious"
"young warrior (folk etymology)"
"farmer, earthworker"
"man from Lucania"
"bright fame"
"broad valley, broad hillside"
"consecrated; worthy of reverence"
"east town"
"one who carries"
"park keeper"
"son of Aeson, the hero who sought the Golden Fleece"
"Lord, have mercy (liturgical)"
"from the Antonius Roman family"
"one who builds with stone"
"dove"
"my messenger, my angel"
"muddy place, ditch"
"fire of the Lord"
Similar sound: These names share phonetic patterns with Cooper — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have English origins, giving them the same cultural heritage as Cooper.
Rhythm: Cooper is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.