Seamus sits next to 3 phonetic neighbors — James, Shamus, and Hamish are the closest matches by sound. Most share Seamus's Irish-rooted cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"supplanter"
"reputation, esteem"
"warrior's estate"
"strong-willed warrior"
"valley, narrow glen"
"broad valley"
"slender, narrow"
"who is like God?"
"universal, whole"
"territory of Owen"
"from the moon"
"winding valley"
"God is gracious"
"green river, fresh water"
"warrior, fighter"
"ancient, enduring, long-lived"
"fair, attractive"
"wealthy protector"
Similar sound: These names share phonetic patterns with Seamus — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Hebrew via Irish origins, giving them the same cultural heritage as Seamus.
Rhythm: Seamus is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.