A feature called the Danish Ditch, sitting near the village of Keel on Achill Island in County Mayo, carries one of those blunt folk-historical labels that were applied across Ireland to earthworks, banks, and ditches whose true origins had been forgotten. In popular tradition, anything ancient and unexplained was liable to be attributed to the Danes, a catch-all term Irish rural communities used for Viking-age raiders, or sometimes simply for shadowy builders from a distant, unspecified past. Whether the earthwork at Keel has any genuine Scandinavian association, or whether the name is a piece of inherited folklore grafted onto a far older feature, is part of what makes it quietly worth noticing.

Ireland has dozens of monuments carrying similar names, and in most cases the "Danish" attribution reflects the long memory of Viking coastal activity rather than any archaeological evidence of Norse construction. Achill Island, with its exposed Atlantic position, was not remote from early medieval sea routes, and the coastline around Keel would have been visible to vessels moving along the western seaboard. Earthen banks and ditches in Ireland can date from almost any period, from the Bronze Age through to early modern land management, and without detailed survey work it is rarely possible to assign a confident date from surface appearance alone. The monument is recorded as a distinct feature at Keel, which at least confirms it has enough physical presence to have been formally noted.