Sy sits next to 3 phonetic neighbors — Cy, Sye, and Si are the closest matches by sound. Most share Sy's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"heard by God"
"something bent or curved"
"near the barns, barn keeper"
"crown, wreath, garland"
"upholder of good, who holds firm the good"
"burnt wine, distilled wine"
"one who follows"
"sea strength, power of the sea"
Similar sound: These names share phonetic patterns with Sy — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Hebrew origins, giving them the same cultural heritage as Sy.
Rhythm: Sy is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.