Regan sits next to 4 phonetic neighbors — Reagan, Keegan, and Brogan are the closest matches by sound. Most share Regan's Irish-rooted cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"little king, of royal descent"
"sword"
"the kamani tree (Calophyllum inophyllum)"
"beauty, goodness"
"bright day"
"fashionable, sharp (modern connotation)"
"healer, to heal"
"place of the Koniag people"
"asked of God, prayed for"
"divine water (Zoroastrian)"
"alder tree, from the grove"
"dweller near ash trees"
"born of laughter, joy"
"skilled leader, one who knows (English surname origin)"
"from the court"
"house guardian"
"moon, moonlight"
"noble, virtuous"
"handsome, well-built, beautiful of form"
"desired, precious one"
"the metal copper"
Similar sound: These names share phonetic patterns with Regan — 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 Regan.
Rhythm: Regan is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.