Avon sits next to 4 phonetic neighbors — Evan, Ivan, and Avin are the closest matches by sound. Most share Avon's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"river"
"twin"
"small holy man"
"son of the pearl (via Margaret's meaning)"
"thankful, God has heard"
"dark one, dark-haired"
"descendant of Raghallach"
"vigor, earnestness, seriousness in battle"
"royal title for kings children (Iberian)"
"Roman clan name Horatius (origin uncertain)"
"victory of the people"
"futility, vanity"
"brewer, one who brews"
"military rank above captain"
"rocky hill town"
"a fast-moving projectile, symbol of speed and ambition"
"son of James, supplanter"
"boar friend"
"silver-wheeled (sky goddess)"
"woodland clearing"
"descendant of Bradach (spirited one)"
Similar sound: These names share phonetic patterns with Avon — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Celtic/Brythonic origins, giving them the same cultural heritage as Avon.
Rhythm: Avon is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.