Heidi sits next to 4 phonetic neighbors — Hyde, Hedy, and Brady are the closest matches by sound. Most share Heidi's German-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"noble, of noble type"
"compound of William (protector) and Joseph (God adds)"
"small fertile land plot"
"old river, ancient waters"
"invented name with La- prefix (the) and Voris (from the ford, Dutch..."
"high, noble, strong"
"fond of horses"
"curved throwing stick, boomerang"
"dweller by a spring or well"
"shield wolf (derived from Randy/Randolph)"
"young bear, small animal"
"shield wolf, brave protector"
"high, noble"
"reborn, born again"
"warm earthy hue; tanned"
"who is like God?"
"label, identifying mark; to touch lightly"
Similar sound: These names share phonetic patterns with Heidi — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old High German origins, giving them the same cultural heritage as Heidi.
Rhythm: Heidi is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.