Allen sits next to 4 phonetic neighbors — Alan, Allan, and Alain are the closest matches by sound. Most share Allen's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"handsome, cheerful"
"exalted father"
"of the Caspian Sea"
"Frankish person"
"son of the red-haired one"
"thunder and lightning"
"horse friend"
"letter J, initial name"
"appointed, placed by God"
"gift of God"
"God is my light"
"spear strength, brave with the spear"
"wolf lover"
"winding valley"
"dragon"
"to heal"
"divine healer"
"thankful, grateful"
"ruler of the people"
Similar sound: These names share phonetic patterns with Allen — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Celtic origins, giving them the same cultural heritage as Allen.
Rhythm: Allen is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.