Phenix sits next to 4 phonetic neighbors — Phoenix, Fenix, and Felix are the closest matches by sound. Most share Phenix's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"dark red, crimson"
"modern coinage; possibly town settlement"
"battle worthy, eager in battle"
"from the east, eastern settlement"
"of the forest, wood (inspired)"
"playful one"
"from the third settlement"
"high, noble, strong"
"grace, favor, thankfulness"
"little one, junior (Vaughn element)"
"young wolf, wolf cub"
"page boy (de Chiel)"
"Eorla's settlement (personal name etymology)"
"creative phonetic variant of Casey"
"creative respelling of Zion (highest point, monument)"
"anointed one"
"little fire"
"short form of Andre/Andrew"
"manly, masculine (as variant of Drew/Andrew)"
"faithful, genuine, true"
"enduring and given by God"
Similar sound: These names share phonetic patterns with Phenix — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Greek phoinix origins, giving them the same cultural heritage as Phenix.
Rhythm: Phenix is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.