Kallen sits next to 5 phonetic neighbors — Callum, Callen, and Callan are the closest matches by sound. Most share Kallen's Irish-rooted cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"powerful in battle"
"thankful, grateful"
"son of Javan, modern invention"
"Roman fort on the River Leir"
"noble lord, feudal warrior"
"forest"
"divine, of the god of wine"
"modern spelling of Coe (jackdaw bird)"
"qualitative time, the fullness of time"
"protector of the people"
"lord (if related to Kyrie)"
"goddess of the hunt and moon"
"little poet, little philosopher"
"Christian cross, symbol of faith"
"gift of God"
"born at dawn, of the light"
"ruler of the people"
"of the wood, forest-born"
"growth, abundance, increase"
"supplanter"
"one who resembles God"
Similar sound: These names share phonetic patterns with Kallen — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Irish Gaelic origins, giving them the same cultural heritage as Kallen.
Rhythm: Kallen is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.