Donovan sits next to 4 phonetic neighbors — Sullivan, Callahan, and Brennan are the closest matches by sound. Most share Donovan's Irish-rooted cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"dark warrior"
"son of the king"
"son of Lawrence"
"sovereign, owner"
"descendant of Dorus, Dorian Greek"
"soldier"
"prince's town"
"son of Ridge"
"charcoal, dark"
"ardor, enthusiasm, fierceness"
"first zodiac sign, new beginnings"
"one who bails, deliverer"
"ruler of the world"
"strife, war"
"possibly from a- (not) + treo (tremble)"
"modern American invented name"
"young dog, whelp"
"leatherworker, craftsman"
"dark man's settlement, coal-black farm"
Similar sound: These names share phonetic patterns with Donovan — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Irish Gaelic origins, giving them the same cultural heritage as Donovan.
Rhythm: Donovan is a 3-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.