Harlen sits next to 3 phonetic neighbors — Harlan, Harley, and Darlen are the closest matches by sound. Most share Harlen's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"rocky land, gray land"
"forefather"
"blessed"
"little fiery one"
"help, strength"
"powerful army"
"atmospheric mist, haze"
"little fire"
"rain, precipitation"
"hunter"
"of the sea (via Marius)"
"happy estate"
"the very greatest"
"prince, leader (from -mir)"
"guardian of prosperity"
"strength, powerful one"
"falling, rhythmic beat"
"prince, commander"
"great, supreme, exalted"
"son of Lars (son of Lawrence)"
"Son of Walter"
Similar sound: These names share phonetic patterns with Harlen — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old English har + land origins, giving them the same cultural heritage as Harlen.
Rhythm: Harlen is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.