Eider sits next to 4 phonetic neighbors — Aiden, Rider, and Edan are the closest matches by sound. Most share Eider's German-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"from the Eider river"
"rest, comfort (when used as variant of Noah)"
"divine presence"
"supplanter, one who follows at the heel"
"strife"
"heir, descendant, beloved"
"the bear"
"lotus, water lily"
"passionate, earnest"
"God-like"
"roofer, one who covers"
"old, wise, of noble birth"
"valley, hollow"
"village of the cross, farm by the cross"
"new house"
"vigor and power"
"home ruler"
"bringer of treasure (gift-bearer)"
"father of peace"
Similar sound: These names share phonetic patterns with Eider — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Germanic/Nordic origins, giving them the same cultural heritage as Eider.
Rhythm: Eider is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.