A number of law codes have in the past been in use in the various Celtic nations since the Middle Ages.While these vary considerably in details, there are certain points of similarity. The Brehon Laws governed everyday life and politics in Ireland until the Norman invasion of 1171 (the word "Brehon" is an Anglicisation of breitheamh (earlier brithem), the Irish word for a judge). The laws were written in the Old Irish period (ca. 600–900 AD) and probably reflect the traditional laws of pre-Christian Ireland.