[Cash-til Ahail] Probably from the Gaelic Caisteal a' Ghabhail, meaning Castle of the Fork, though the second word could be a corruption of Ha Fjell, Norse for High Fell.
The main winter interest on Caisteal Abhail is on the north side of Ceum na Caillich (The Witch's Step), the rocky peak on the mountain's east ridge. This ridge is also a pleasant scrambly route to the summit of Caisteal Abhail, regardless of conditions underfoot.