Cythraul

Cythraul is an old Welsh word, still in everyday use, meaning 'devil' or, with a capital letter, the Devil, probably deriving from Latin 'Contrarius', 'the Opposer, Enemy'. Contr- would go to Welsh cythr- straightforwardly according to historical phonology, and the form 'cythraul' not *cythraur is the result of dissimilation. It is likely to be an early Christian borrowing from Ecclesiastical Latin, like numerous other words in the Welsh and Irish languages. Diawl (from Latin diablos) is usually used for the Devil (Satan) today, cythraul usually being used as a pejorative, e.g. "y cythraul bach!" '(you) little devil/rascal!'.

Modern Druidic interpretation
Cythraul has been identified as a 'spirit of Chaos' by some modern Druids, an interpretation which dates back to Iolo Morganwg's Barddas. According to this view, "Cythraul" may be used to designate the same condition of primordial chaos or limitlesness which appears in, for example, Plato's Timaeus at 30A or Genesis 1. As the contemporary Druidic tradition springs from the Druid Revival, which began in the 18th century, and is unconnected with the ancient Druids except in viewing the latter as a source of inspiration, it is perfectly justified in this interpretation.