Cai sits next to 4 phonetic neighbors — Kai, Kay, and Cay are the closest matches by sound. Most share Cai's Welsh cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"rejoice, delight"
"lime tree hill"
"short form of Orlando, famous land"
"hollow, empty"
"peace"
"Moorish, dark-complexioned"
"devotee of Saint Columba"
"crown, wreath"
"gift"
"wild, untamed nature"
"from Galloway"
"cliff settlement"
"a day's travel, expedition"
"dear, beloved"
"green/fresh river"
"rocky stream"
"held by the heel"
"pierce the valley"
"boar-friend, warrior companion"
"from the high woodland clearing"
"brave people, bold folk"
Similar sound: These names share phonetic patterns with Cai — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Latin via Welsh origins, giving them the same cultural heritage as Cai.
Rhythm: Cai is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.