Kullen sits next to 5 phonetic neighbors — Cullen, Collin, and Kullan are the closest matches by sound. Most share Kullen's Scandinavian cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"hill, ridge, small summit"
"the greatest one, supreme ruler"
"from the village of Estry in Normandy, France"
"emperor, ruler"
"frenzied, poetic inspiration"
"God is gracious"
"bear man, noble bear"
"joy, song of life"
"triumph, conquest"
"farm on the ridge"
"to shout, to sing joyfully"
"lotus flower"
"mind, intellect, spirit"
"World ruler (from Donald prefix Don-)"
"forest meadow"
"Resolute protection; will-helmet"
"warrior of the sea"
"shield rim"
"volcanic black glass"
"settlement among the undergrowth, brushwood farm"
Similar sound: These names share phonetic patterns with Kullen — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Scandinavian origins, giving them the same cultural heritage as Kullen.
Rhythm: Kullen is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.