Jansen sits next to 4 phonetic neighbors — Jensen, Jason, and Janson are the closest matches by sound. Most share Jansen's Dutch-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"son of Jan (John)"
"God is gracious"
"son of the peacemaker"
"Wine's hill, friend's hill"
"intelligent one"
"from Britain, a Briton"
"noble, virtuous"
"deer, little deer"
"love, romantic feeling"
"hill"
"rope maker"
"gift of God"
"white, silver (ancient root)"
"American creative variation"
"variant of Tyson, firebrand"
"son of Hans (John)"
"will-helmet"
"of uncertain meaning, possibly healer"
"beloved friend, dear companion"
"beloved of God, beloved of Yahweh"
"healer"
Similar sound: These names share phonetic patterns with Jansen — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Dutch origins, giving them the same cultural heritage as Jansen.
Rhythm: Jansen is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.