Heidi sits next to 4 phonetic neighbors — Sadie, Hailey, and Hedy 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 kind"
"oath of God"
"dry (referring to the plant's preferred soil)"
"small bird (wren)"
"work-power, industrious strength"
"beautiful, attractive, pleasant"
"prosperous in war"
"industrious ruler"
"life's path, passage"
"bitter, beloved"
"young ceremonial attendant"
"white or bright settlement"
"cloud"
"one who bears palm branches"
"champion, one who attains"
"crooked nose"
"worthy of love, she who must be loved"
"holly tree"
"tailor, cloth-cutter"
"descendant of Leannán"
Similar sound: These names share phonetic patterns with Heidi — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Germanic 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.