Cullen sits next to 5 phonetic neighbors — Colin, Calvin, and Cullan are the closest matches by sound. Most share Cullen's Irish-rooted cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"at the holly trees"
"Harry's son, son of the ruler"
"modern invented name"
"gift"
"strength, permanence"
"loud revelry"
"rock hill, old hill"
"bold counsel, brave advisor"
"tournament fighter"
"carrier, one who bears"
"resolute protector"
"narrow strait"
"bright fame"
"wealthy guardian, guardian of fortune"
"divine presence"
"bookbinder, scribe"
"always, at all times"
"open grassy land"
"prince, chief"
"son of the red warrior"
Similar sound: These names share phonetic patterns with Cullen — 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 Cullen.
Rhythm: Cullen is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.