A cashel is a ringfort built from dry-stone walling rather than earthen banks, a construction method common in the west of Ireland where stone was abundant and easily worked. These circular enclosures were typically built during the early medieval period, roughly between the fifth and twelfth centuries, and served as enclosed farmsteads for a single family or small community, offering protection for livestock and household alike.

Askillaun itself is a remote coastal townland, and the presence of a cashel there speaks to a pattern of early settlement along Ireland's western seaboard that was far denser than the emptiness of the modern landscape might suggest. Early medieval farming communities were drawn to coastal areas for their relatively mild climate, access to marine resources, and the manageable terrain around inlets and bays. Stone ringforts of this type were not fortifications in any military sense but rather the ordinary domestic architecture of their era, and thousands of them survive across Ireland in varying states of preservation, some reduced to a scatter of stones, others with walls still standing to considerable height.

Beyond the classification and the general location, the documentary record for this particular cashel is sparse. What can be said with confidence is that it belongs to a category of monument that anchors the west Mayo coastline to a period of settlement largely invisible in the written record, known to us almost entirely through what remains on the ground.