Callen sits next to 4 phonetic neighbors — Callan, Kalen, and Allen are the closest matches by sound. Most share Callen's Scottish cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"battle mighty, warrior"
"unity, one; the highest rank"
"gentle strength"
"majestic one"
"land of the Norsemen"
"strong, virtuous, honorable"
"heavenly flower, heavenly lei"
"long journey, epic voyage"
"famous warrior"
"valley (glen) + feminine suffix"
"beautiful, honest (in Japanese tradition)"
"reddish-brown, auburn color"
"Yahweh has shown favor"
"bright, shining"
"bright-headed, fair"
"dearly loved one"
"supplanter, one who follows at the heel"
"freckled, speckled"
"pipe, conduit"
"new, new star"
Similar sound: These names share phonetic patterns with Callen — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Scottish Gaelic origins, giving them the same cultural heritage as Callen.
Rhythm: Callen is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.