Declyn sits next to 4 phonetic neighbors — Declan, Declun, and Daklin are the closest matches by sound. Most share Declyn's Irish-rooted cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"man of prayer, full of goodness"
"oak tree by the pool or stream"
"victory of the people"
"great tide"
"son of the pearl (via Margaret's meaning)"
"craftsman, smith"
"he will judge"
"handsome, comely, gentle"
"meadow, pasture (possible alternate)"
"defender of men"
"son of Jack"
"lotus flower, love"
"a fast-moving projectile, symbol of speed and ambition"
"God has helped"
"gift of God, godlike"
"God is salvation"
"master, mister (honorific)"
"praised, God will be praised"
"descendant of Bradach (spirited one)"
"of the mountain"
Similar sound: These names share phonetic patterns with Declyn — 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 Declyn.
Rhythm: Declyn is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.