Mattis sits next to 3 phonetic neighbors — Matthias, Mattias, and Maddox are the closest matches by sound. Most share Mattis's German-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"gift of God"
"descendant of the earl"
"defender of the people, protector of men"
"one who burns, charcoal burner, distiller"
"bright north, famous northerner"
"the greatest"
"from Berlin (swampy area)"
"dwellers in wooded hills"
"one who bakes (occupational surname)"
"short form of Tobias"
"day"
"lord of the estate, powerful at home"
"stern, severe, serious"
"resolute protector, determined guardian"
Similar sound: These names share phonetic patterns with Mattis — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Hebrew Mattityahu origins, giving them the same cultural heritage as Mattis.
Rhythm: Mattis is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.