Likely a modern blend of Erin and Lynn, evoking Ireland and a soft feminine ending.
Erilyn is a graceful compound name that braids together two distinct geographic and linguistic traditions. The first element, Eri-, derives from Éire, the Irish word for Ireland itself, used in the poetic address Éirinn — "to Ireland" — that appears in countless songs and laments for the island nation. To bear an Erin-rooted name is to carry a tiny piece of that storied island, its green hills and complicated history encoded phonetically in the name's opening sound.
Erin became widely popular in the United States during the latter half of the 20th century, particularly among families of Irish descent. The -lyn suffix comes from the Welsh llyn, meaning "lake" — a word that also enters the name Evelyn, Carolyn, and Jacquelyn. It is a sound associated in American naming with softness, femininity, and a vaguely Celtic-adjacent musicality, even when parents are not consciously thinking of Welsh geography.
Together, Erilyn evokes a landscape: Ireland meeting Wales across the Celtic Sea, two island traditions meeting in a single name. Erilyn belongs to the large family of compound feminine names — Emmalyn, Adalyn, Rosalyn — that dominated American naming trends from the 1990s through the 2010s. Within that family, it has a distinctly literary and geographic quality. Writers and readers often gravitate toward it, sensing that the name carries the breath of old stories without being bound to any single one.