Kasper sits next to 4 phonetic neighbors — Casper, Jasper, and Kaspar are the closest matches by sound. Most share Kasper's Scandinavian cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"treasurer, keeper of treasure"
"hollow land (alternative)"
"fire"
"one who illuminates, enlightener"
"his peace"
"famous ruler"
"who is like God? (rhetorical — implying no one)"
"eagle"
"consecrated by augury"
"from the, of the family"
"brave in counsel"
"he judged, he governed"
"free man, strong man"
"honor-friend"
"rowan tree"
"peaceful ruler"
"graced by God"
"rune letter, inscribed symbol"
Similar sound: These names share phonetic patterns with Kasper — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Persian origins, giving them the same cultural heritage as Kasper.
Rhythm: Kasper is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.