Penn sits next to 5 phonetic neighbors — Ben, Len, and Ken are the closest matches by sound. Most share Penn's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"hill, headland, enclosure"
"lord, master (via Kyrie element)"
"noble friend"
"possessor, acquirer"
"eagle land"
"delight, paradise (as in Eden)"
"handsome, gentle"
"wealthy guardian"
"stone of help"
"sword people, stone-knife people"
"miracle of God"
"modern invented name combining Jay and -ven"
"child of Zeus (folk etymology)"
"hollow, seething pool"
"island meadow, land near water"
"modern invented name"
"son of the rock"
"land by the road"
"hollow, small cavity"
"hill"
Similar sound: These names share phonetic patterns with Penn — 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 Penn.
Rhythm: Penn is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.