Koy sits next to 3 phonetic neighbors — Roy, Coy, and Koi are the closest matches by sound. Most share Koy's Dutch-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"victorious people"
"oak tree"
"son of the devotee of Saint Fillan"
"friend, ally"
"beloved"
"noble, princely"
"the white one, fair"
"moonlight; of the moon"
"son of Hendrik"
"strong, great warrior"
"God is gracious"
"guardian, watchman"
"handsome, well-born"
"fighter, battle"
"gray, silver-haired"
"warrior, gift of God"
"modern nature name variant"
"valley of the River Kent"
"large homestead, big village"
"God is gracious (from Hebrew Yochanan via Welsh)"
Similar sound: These names share phonetic patterns with Koy — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Greek via Dutch origins, giving them the same cultural heritage as Koy.
Rhythm: Koy is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.