Colby sits next to 4 phonetic neighbors — Cody, Koby, and Corby are the closest matches by sound. Most share Colby's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"dark man's settlement, coal-black farm"
"to rule as monarch"
"sun, like the sun"
"bold power, chief ruler"
"settlement of the prince"
"God has heard"
"plum tree (unrelated homophone)"
"beam of light"
"wolf lover"
"hollow, empty"
"people's victory"
"modern coined name, son of Bray"
"free man"
"son of Otto"
"sovereign, owner"
"farm settlement of Dudda"
"land where rye is grown"
"famous warrior"
"free man"
"modern American invented name"
"he who holds firm the good"
Similar sound: These names share phonetic patterns with Colby — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old Norse origins, giving them the same cultural heritage as Colby.
Rhythm: Colby is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.