SGAIRT FHUATHACH, 167, a horrible weird uncanny scream, from others than the visible denizens of the terrestrial globe.
FUATH, VII 41, a spirit of terror.
Sgairt, among many other meanings, can be a shriek, and Dwelly also has fuathach as meaning spectral, demoniacal (as well as hateful, abhorrent, averse).
Sgairt has also been recorded in Skye as meaning “a prophetic voice heard on rare occasions by certain individuals. A sort of ‘second hearing’.”