From a name of a farm in the immediate vicinity -- Dunree, in Gaelic Dun-righ, signifying the king's stronghold -- it is inferred that the fort was distinguished by a royal appellative.
[..] In former times, Cassillis Downans was regarded as a favourite haunt of the fairies of Ayrshire, and a popular tradition still exists illustrative of their peculiar attachment to the locality. The old house of Cassillis, it is said, was originally intended to have occupied a site on the top of the hill, but the fairies were so much opposed to this that they invariably demolished at night what had been built during the day -- removing the stones and other material to the spot where the castle now stands -- until the proprietor, convinced of the folly of contending with his invisible opponents, at length gave up the contest.
Dowan's Hill is a fort with double ramparts. It gets a mention in Robert Burns' poem "Halloween":
Upon that night when fairies light
On Cassillis Downans dance
Or owre the lays in splendid blaze
On sprightly coursers prance;
Or for Colean the rout is ta'en
Beneath the moon's pale beams;
There up the cove, to stray and rove
Amang the rocks and streams.
Burns wrote in a 1787 letter: "In my infant and boyish days too, I owed much to an old maid of my Mother's, remarkable for her ignorance, credulity and superstition. --She had, I suppose, the largest collection in the county of tales and songs concerning devils, ghosts, fairies, brownies, witches, warlocks, spunkies, Kelpies, elf-candles, dead-lights, wraiths, apparitions, cantraips, giants, inchanted towers, dragons, and other trumpery.
--This cultivated the latent seeds of Poesy; but had so strong an effect on my imagination, that to this hour, in my nocturnal rambles, I sometimes keep a sharp look-our in suspicious places; and though nobody can be more sceptical in these matters than I, yet it often takes an effort of Philosophy to shake off these idle terrors."
found in Robert Burns' Satires and the Folk Tradition: "Halloween"
South Atlantic Bulletin, Vol. 32, No. 4. (Nov., 1967), pp. 10-13.