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"
"pure, clear"
"truthfulness, sincerity"
"superior, more desirable"
"daughter of Helen (by association)"
"isle of apples"
"God is gracious"
"happiness, fortune"
"traveler through the forest"
"great queen"
"alive, living, lively"
"land of the Welsh, Wales"
"farmer, earth-worker"
"reed clearing, cleared wood"
"star sun"
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.