Nigel sits next to 4 phonetic neighbors — Nile, Neil, and Nigel are the closest matches by sound. Most share Nigel's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"champion (from Old Irish Niall)"
"armed host, military force"
"powerful, bright-headed warrior"
"spear servant"
"acquired, possessed"
"Majestic, inspiring reverence"
"protector, helper of mankind"
"son of the spear-ruler (Gerald = Geirald)"
"secluded valley"
"God is gracious"
"belonging to God"
"bent river"
"universal ruler"
"roe deer forest, deer wood"
"vigilant in war"
"the very greatest"
"Lukes town"
"gate attendant, herald"
"sharp hill, ridge"
"battlefield (poetic extension)"
Similar sound: These names share phonetic patterns with Nigel — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old Irish via Norman Latin origins, giving them the same cultural heritage as Nigel.
Rhythm: Nigel is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.