Galen sits next to 4 phonetic neighbors — Gavin, Glen, and Gale are the closest matches by sound. Most share Galen's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"calm, tranquil"
"strength, my strength"
"gift of God"
"thunder, of Thor"
"bold, brave, daring"
"healer"
"possibly from Basque or Persian place names"
"heart, mind, spirit (from Hugh)"
"God is my light, my flame is Yahweh"
"speckled, or from the bridge settlement"
"named after the Parisii Gallic tribe"
"of January, born in January"
"light, radiance"
"modern invented name"
"dark, dark-featured"
"of Shawn (Da prefix intensifier)"
"handsome, gentle"
"settlement on the ridge, hilltop estate"
"gift of splendor, bounty"
"faithfulness, devotion, steadfast allegiance"
"highest point in the sky, directly overhead"
Similar sound: These names share phonetic patterns with Galen — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Greek origins, giving them the same cultural heritage as Galen.
Rhythm: Galen is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.