Kain sits next to 4 phonetic neighbors — Kane, Cain, and Cane are the closest matches by sound. Most share Kain's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"spear"
"cloud"
"bright, radiant"
"God has given"
"from Chester (place name)"
"rush plant (marsh grass)"
"son of Gilbert, son of Gib"
"lord, father, sovereign"
"guardian spirit, divine being"
"victory of the people"
"Caesar, imperial leader"
"son of Jack"
"jewel, gem"
"to listen, to spy out"
"lion"
"thankful, grateful"
"son of Otto, helpful"
"of the sea (possible etymology)"
"green river, fresh water"
"scarce, seldom"
"scholar"
Similar sound: These names share phonetic patterns with Kain — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Hebrew origins, giving them the same cultural heritage as Kain.
Rhythm: Kain is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.