Sydney sits next to 3 phonetic neighbors — Sidney, Sydni, and Cydney are the closest matches by sound. Most share Sydney's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"wide island"
"manly, masculine (as variant of Drew/Andrew)"
"distinguished leader"
"resolute will, helmet of will"
"of the night"
"descendant of Comhradha"
"tailor, cloth cutter"
"town of stone"
"alder tree, from the grove"
"beloved of Yahweh"
"manly, brave, strong (via Andre/Andreas)"
"named after father"
"dweller at the white enclosure"
"strong worker's son"
"Dutch/Scandinavian spelling of Isaac from Yitzchak"
"treasurer, keeper of treasure"
"craftsman, skilled maker"
"gift from God, he who is sent"
"friend of God"
"from the Roman city of Lindum"
Similar sound: These names share phonetic patterns with Sydney — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old English sid (wide) and eg (island) origins, giving them the same cultural heritage as Sydney.
Rhythm: Sydney is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.