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)"
"yellow, fair"
"gift of God"
"God is gracious"
"dark blue"
"knowledge, good judgment, deep understanding"
"from the Roman Gens Terentia"
"hilltop settlement of the friend"
"narrow strait"
"lion"
"healer"
"noble, virtuous"
"who is like God?"
"son of Rhys, ardor and enthusiasm"
"gift of God, gift of Yahweh"
"diminutive of Judith, praised woman"
"son of Cadan, fighter"
"little gift of God"
"money, currency"
"noble born"
"dedicated to Mars (god of war)"
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.