Tiernan sits next to 4 phonetic neighbors — Kiernan, Tierney, and Brennan are the closest matches by sound. Most share Tiernan's Irish-rooted cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"lord, chief, ruler"
"God is gracious"
"young, youthful"
"young warrior"
"Yahweh is gracious"
"descendant of Bradan (salmon)"
"little deer, fawn"
"from Kelso (place name)"
"oak grove"
"from the River Clyde"
"born of fire, handsome chief (via Kenneth/Cionaodha)"
"worker, one who builds"
"ocean, sea (from Kai)"
"white heart, blessed heart"
"little fire"
"brave ruler, powerful leader"
"spear, warrior"
"dark one, dark-haired"
"descendant of Ceallachan"
Similar sound: These names share phonetic patterns with Tiernan — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old Irish origins, giving them the same cultural heritage as Tiernan.
Rhythm: Tiernan is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.