Keller sits next to 4 phonetic neighbors — Kellan, Kellor, and Keller are the closest matches by sound. Most share Keller's German-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"cellar keeper, wine steward"
"Hawaiian form of Matthew"
"green river, fresh water"
"army guard, protecting warrior"
"one who observes, explorer"
"modern invented name"
"modern invented name, valley dweller (from -den suffix)"
"king, ruler"
"descendant of Aodh (fire)"
"son of Dubhagan (little dark one)"
"new house"
"pierce the valley"
"modern invented name, possibly dark one"
"lord, father, sovereign"
"sacred, belonging to the divine"
"pledge, oath"
"qualitative time, the fullness of time"
"people's power"
"dove"
"peaceful ruler"
Similar sound: These names share phonetic patterns with Keller — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have German origins, giving them the same cultural heritage as Keller.
Rhythm: Keller is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.