Keir sits next to 5 phonetic neighbors — Kier, Kiir, and Ciarán are the closest matches by sound. Most share Keir's Scottish cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"dark one, dark-complexioned"
"red-haired king"
"from the gray hill"
"little red one"
"wolf cub"
"from the southern lands"
"God is gracious"
"sharp, intelligent"
"gentle birth, beloved"
"son of the renowned ruler"
"westward, to the west"
"dark, full; complete darkness"
"defender of men"
"son of the wave, born of the sea"
"brave traveler"
"A dark image or form following a person or object"
"landholder, lord"
"cloud"
Similar sound: These names share phonetic patterns with Keir — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Scottish Gaelic ciar origins, giving them the same cultural heritage as Keir.
Rhythm: Keir is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.