Madyn is a modern spelling of Madeline or Madison-style names, used chiefly for contemporary sound and style.
Madyn is a modern phonetic respelling of Madeline (or Madison), names with quite different ancestries that have converged in popular imagination. Madeline descends from the Greek Magdalene — literally "woman from Magdala," a fishing town on the Sea of Galilee — and entered Western Europe through Mary Magdalene, one of Christianity's most complex and enduring figures. Magdalene became Madeleine in French, Madeline in English, and eventually the diminutives Maddie and Mady.
Ludwig Bemelmans immortalized the French spelling in his beloved 1939 picture-book series, giving Madeline a literary afterlife inseparable from Parisian adventure and a little girl in two straight lines. Madison, by contrast, is a transferred English surname meaning "son of Maud" (itself a form of Matilda, "mighty in battle"), which vaulted onto the girls' name charts in the United States after the 1984 film Splash featured a mermaid who took her name from Madison Avenue. The two streams — Madeline and Madison — pooled together in the 1990s and 2000s, producing a wave of Maddies, Maddys, and Madyns.
The spelling Madyn is a distinctly twenty-first century development, dropping the terminal "e" or "ison" to create something that looks both ancient and futuristic on the page. It appeals to parents who want the familiar sound of "MAY-din" while giving their child a visually distinctive name. The variant signals a generational shift in how American parents think about spelling as an act of individuation.