Trystan sits next to 4 phonetic neighbors — Tristan, Tristen, and Tristin are the closest matches by sound. Most share Trystan's Welsh cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"tumult, noise of battle"
"possibly related to Zaid (growth, increase)"
"falcon, bird of prey"
"age, era, vast expanse of time"
"from the ford, river crossing"
"fiery one"
"from the heath, heathen land"
"fortunate protector"
"Southern American place name as given name"
"ruler, one who rules"
"flower bud casing"
"beloved (possibly influenced by love)"
"will-helmet (determined guardian)"
"great, kingly"
"songbird, free spirit"
"speckled, freckled"
"Yahweh remembers"
"desert world (fictional)"
"of the sea, marine"
"God is my flame"
"supplanter"
Similar sound: These names share phonetic patterns with Trystan — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Celtic 'drest' origins, giving them the same cultural heritage as Trystan.
Rhythm: Trystan is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.