Sianni sits next to 5 phonetic neighbors — Sienna, Siani, and Shani are the closest matches by sound. Most share Sianni's Welsh cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"God is gracious"
"happiness, fortune"
"otherworldly paradise"
"the other Aenor / bright one"
"pure, clear"
"dweller near the reed meadow"
"superior, more desirable"
"land of the Welsh, Wales"
"immortal"
"daughter of Helen (by association)"
"truth"
"friend, companion"
"pear tree"
"from the Caecilius family"
Similar sound: These names share phonetic patterns with Sianni — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Hebrew Yochanan via Welsh Siân origins, giving them the same cultural heritage as Sianni.
Rhythm: Sianni is a 3-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.