Kelly sits next to 4 phonetic neighbors — Kelley, Kell, and Kellan are the closest matches by sound. Most share Kelly's Irish-rooted cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"bright-headed warrior"
"strong like a boar"
"cypress tree"
"strong, healthy"
"broad valley"
"gift of God, God is salvation"
"little fire (from Irish aodh)"
"he to whom it belongs, messianic title"
"youth, young warrior"
"supplanter, one who replaces another"
"like steel, strong and hard"
"modern invented name, possibly dark one"
"from the River Irvine"
"bright, clear, famous"
"rich friend"
"descendant of the courageous one"
"thunder ruler"
"great house"
"eagle power, eagle ruler"
"modern coined name, variant of Kyson"
"lake dweller, from the lake"
Similar sound: These names share phonetic patterns with Kelly — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old Irish origins, giving them the same cultural heritage as Kelly.
Rhythm: Kelly is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.