The Irish "lios" refers to an enclosure, typically the circular earthen bank and ditch that once defined a farmstead or defended settlement in early medieval Ireland, and "gross" likely derives from "gras" or a related form suggesting a grassy place. That the townland name and the monument type should echo each other so precisely is not unusual in Mayo, where the landscape has been read and re-read in Irish for centuries, but it does give the site a pleasing self-referential quality, as if the place announced itself long before anyone came to record it formally.

Enclosures of this kind, sometimes called raths or ring-forts depending on their construction and context, are among the most common archaeological monument types in Ireland, yet each one represents a particular household, a particular moment of settlement, a decision by someone to dig and pile earth and mark out a boundary between inside and outside. Mayo has hundreds of them, distributed across bogland, hillside, and improved farmland alike, and many survive only as cropmarks or slight rises in a field that a passing walker might not look at twice. Lisnagross sits in this category of places that are recorded, named, and present in the land, but whose specific details remain largely unexamined in the public record.