Hardin sits next to 4 phonetic neighbors — Harlan, Hayden, and Harden are the closest matches by sound. Most share Hardin's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"valley of the hares"
"I am, self-existence, declaration of being"
"hazel valley dweller"
"modern blended name"
"from the moon"
"world ruler"
"peace power"
"crooked nose; bent river"
"lime tree hill"
"scarce, seldom"
"son of the earth"
"avenger, one who does not forget"
"venerable, revered"
"path to the sea"
"from Kent, the English county"
"destined, determined"
"one touched by good fortune"
"name of God"
"a large inland body of water"
"hollow land (alternative)"
"crooked hill"
Similar sound: These names share phonetic patterns with Hardin — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old English origins, giving them the same cultural heritage as Hardin.
Rhythm: Hardin is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.