River sits next to 3 phonetic neighbors — Ryder, Silver, and Riviere are the closest matches by sound. Most share River's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"flowing body of water, stream"
"merciful, gentle"
"from the valley of water"
"from Sebastia, venerable"
"Scottish form of John, gift of God"
"treasurer, keeper of treasure"
"my God is Yahweh"
"courageous, valiant"
"Little hollow; from the little hollow place"
"God is gracious (via Jack, from John)"
"son of Carsun, dweller near the marsh"
"From the English surname 'son of the grieve (estate overseer)' or '..."
"tall, imposing one"
"little fire"
"defender of men"
"group, team, company of people"
"of the forest"
"one who walks"
"soldier"
"man, full-grown man"
"crooked, enclosed valley"
Similar sound: These names share phonetic patterns with River — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old French origins, giving them the same cultural heritage as River.
Rhythm: River is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.