Achall is from the Old Irish achlaim (lament). **In Irish mythology, Achall was the daughter of Cairbre Nia Fer, sister of Erc** — **she died of grief at her brother's death by Cú Chulainn**. The Hill of Achall, **modern Hill of Skreen near the Hill of Tara**, is named for her burial mound.
Featured in the Ulster Cycle.
Achall reduces to nine — the number of Irish grief.