What is "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!'.