Berlyn sits next to 4 phonetic neighbors — Berlin, Brynn, and Evelyn are the closest matches by sound. Most share Berlyn's Slavic via German-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"from Berlin; swamp, marsh (Slavic root of Berlin)"
"slender, beautiful"
"land of the Britons"
"enduring inheritance, what is left behind"
"gracious gift of God"
"boomerang (curved throwing stick)"
"white wave"
"lake (from Welsh -lyn element)"
"amber jewel"
"sea village"
"of the birds, bird-like"
"holy day, day of celebration"
"brave, valiant"
"descendant of Raghaillach"
"dark beauty, dark-complexioned one"
"plaything (original Latin sense)"
"life, living"
"grace, favor"
"they are enough, they are satisfied"
"valley with a crest"
"bright valley"
Similar sound: These names share phonetic patterns with Berlyn — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Slavic via German origins, giving them the same cultural heritage as Berlyn.
Rhythm: Berlyn is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.