Cydney sits next to 5 phonetic neighbors — Sydney, Sidney, and Cindy are the closest matches by sound. Most share Cydney's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"wide island"
"children of deaf adults (modern acronym)"
"chalk wharf, landing place on the Thames"
"moon, moon goddess"
"little olive"
"Work-power; industrious leader"
"defender of mankind"
"ivory-white, creamy white"
Similar sound: These names share phonetic patterns with Cydney — 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 Cydney.
Rhythm: Cydney is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.