Thuan sits next to 3 phonetic neighbors — Tuan, Swan, and Quan are the closest matches by sound. Most share Thuan's Vietnamese/Chinese-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"smooth, favorable, agreeable"
"evenness of mind, inner balance"
"lovestruck, mad with love, infatuated"
"beam of light, torch"
"peaceful ruler"
"phonetic variant of Monet (French surname/artist name)"
"invented name with feminine suffix"
"she who remains, the everlasting one"
"to sing, to shout for joy, to cry out in praise"
"honey bee"
"narrow mountain valley"
"pure, noble"
"God is gracious"
"ewe, female sheep"
"God is gracious, little wise one"
"lily"
"original American creation (likely influenced by names meaning God ..."
Similar sound: These names share phonetic patterns with Thuan — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Vietnamese/Chinese origins, giving them the same cultural heritage as Thuan.
Rhythm: Thuan is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.