Blanche sits next to 3 phonetic neighbors — Blanc, Blanch, and Branch are the closest matches by sound. Most share Blanche's French-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"white, fair, bright"
"God is good"
"Italian noble house name"
"lavender plant, purple flowering herb"
"Alert; lively; quick"
"supplanter, God will establish"
"people, folk (from Old High German diot, related to Dietrich)"
Similar sound: These names share phonetic patterns with Blanche — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have French origins, giving them the same cultural heritage as Blanche.
Rhythm: Blanche is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.