Mills sits next to 3 phonetic neighbors — Miles, Ellis, and Will are the closest matches by sound. Most share Mills's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"dweller by the mills, mill worker"
"God is gracious"
"lordly, masterful"
"second of twins"
"valley dweller"
"dark blue"
"Italian form of John"
"one who heals"
"healer, physician"
"fire of Yahweh"
"rough, fierce (diminutive)"
"gift from God (popular interpretation)"
"goodness of God"
"lordly, master (via Cyril)"
"from the sheep settlement, from Skipton"
"wolf-like, fierce hunter"
"modern invented name, lively"
"modern invented name, variant of Cole/Colson"
"sword people, stone-knife people"
"of uncertain meaning, possibly healer"
"strength, power, courage"
Similar sound: These names share phonetic patterns with Mills — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old English origins, giving them the same cultural heritage as Mills.
Rhythm: Mills is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.