Nix sits next to 4 phonetic neighbors — Nick, Nicks, and Knox are the closest matches by sound. Most share Nix's Germanic cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"water sprite, water spirit"
"divine protection"
"evergreen flowering shrub of the Mediterranean"
"to tame, subdue"
"beloved friend, gentle one"
"quality, excellence of character"
"supplanter, held by the heel"
"Red-haired"
"companion, friend (Old English origin)"
"Son of Otto"
"rich, wealthy"
"fortunate, prosperous"
"modern compound: Mc (son of) + Aiden (little fire)"
"loved, beloved"
"from the Afton river"
"victory of the people (through Nicholas derivation)"
"earl, nobleman"
"variant of Amal, meaning work or action"
"divine gift (blended)"
"cheerful, lively, in high spirits"
"he causes pain, born in sorrow"
Similar sound: These names share phonetic patterns with Nix — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Germanic origins, giving them the same cultural heritage as Nix.
Rhythm: Nix is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.