Atreyu sits next to 3 phonetic neighbors — Tre, Drayco, and Arayu are the closest matches by sound. Most share Atreyu's German-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"invented name; possibly son of the fearless one"
"I am, self-existence, declaration of being"
"scarce, seldom"
"stubborn one"
"young dog, whelp (strength and loyalty)"
"little rock"
"elf ruler"
"beloved, dear one"
"alive, vital"
"lake dweller, from the lake"
"crew, team"
"huckleberry berry plant"
"descendant of Riagán"
"creative sound combination (no definitive meaning)"
"divine, of the god of wine"
"sculptor, craftsman"
"little fire"
"deep blue color"
"jet black, black gemstone"
"jewel, gem"
"brave as a wild boar"
Similar sound: These names share phonetic patterns with Atreyu — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Fictional (Michael Ende, 1979) origins, giving them the same cultural heritage as Atreyu.
Rhythm: Atreyu is a 3-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.