Darwin sits next to 3 phonetic neighbors — Darren, Dara, and Marvin are the closest matches by sound. Most share Darwin's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"dear friend"
"night"
"Island (from the Scottish island of Tiree)"
"tuft, bump, rounded protrusion"
"lake, pool"
"feminized form of Burl with melodic -line suffix"
"resolute protector"
"elf counsel (via Alfrid)"
"joyful round song"
"God is gracious (from Jean component)"
"noble strength (via Audrey root)"
"alder tree grove (from Gaulish via Vernon)"
"the dawn, daybreak"
"noble one, of aristocratic birth"
"Variant of Joan/Joanne, from Hebrew Yohanan meaning God is gracious..."
Similar sound: These names share phonetic patterns with Darwin — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old English origins, giving them the same cultural heritage as Darwin.
Rhythm: Darwin is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.