The mountain contains several caves and swallow-holes including Pollnagollum (Slieve Rushen) and Tory Hole which are a popular destination for potholers, both situate in Legavreagra townland.

[2] The earliest surviving mention of the name occurs in the Lebor Gabála Érenn or Book of Invasions (c.1100) which lists the battles fought against the Vassal Tribes of Ireland by the high-king Túathal Techtmar in c.76 A.D.- He fought the battle of Raissen against Roiscderg of the kingship of Omrann,[3] (Ro-fích cath Raissen fri Roiscderg ríge Omrann).

Another early mention is in the Annals of the Four Masters for the year 1111 AD- A predatory excursion was made by Toirdhealbhach Ua Conchobhair and he plundered Tearmann-Dabheog.

Another predatory excursion was made by him; and he plundered as far as Beann-Eachlabhra, Sliabh-Ruisen and Loch-Eirne, (Creach lá Toirrdhealbhach Ua c-Conchobhair, go ro aircc Termann Dá Bheócc.

Another raid by him in which he plundered up to Binaghlon and Slieve Rushel and Lough Erne, (Crech la Tairrdelbach O Concobair, cor' airg Termund Da Beoóc.

Another raid by him and he plundered to Benn Eclapra and to Sliab Rusen to Loch Érne, (Creach la Toirrdealbach h. Concupair gur airg Termann Dabeoc.

[8] In the 1609 Plantation of Ulster, Slieve Rushen formed part of lands which were granted to John Sandford of Castle Doe, County Donegal by letters patent dated 7 July 1613 (Pat.