Kelvin sits next to 3 phonetic neighbors — Kevin, Melvin, and Gavin are the closest matches by sound. Most share Kelvin's Scottish cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"from the River Kelvin, narrow river"
"illuminance unit"
"one who cares for others"
"fair administration of law"
"earthly, of the earth"
"vigilant, watchful"
"city of the moon"
"God-like"
"man, husband (older Germanic sense)"
"battle chieftain (Cerdic interpretation)"
"spear warrior"
"wealthy gift"
"dark-complexioned son"
"barrel maker, cask craftsman"
"skill acquired through experience"
"wealthy guardian, guardian of fortune"
"from the marshy plain"
"son of fire"
"son of the firebrand"
"from Sebaste"
"at the holly trees"
Similar sound: These names share phonetic patterns with Kelvin — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Brythonic Celtic origins, giving them the same cultural heritage as Kelvin.
Rhythm: Kelvin is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.