This name derives from the Proto-Brythonic, Old Welsh and Old Irish root: “*kom-brogos > *brogi > combrog > mruig / mroga > *mrogi”, meaning “fellow countryman, compatriot, Welshman > country, territory”. The name "Cambria" lives on in much contemporary literature. It is also used in geology to denote the geologic period between around 542 million years and 488.3 million years ago; in 1835 the geologist Adam Sedgwick named this geological period the Cambrian, after studying rocks of that age in Wales. Camber, also Kamber, was the legendary first king of Cambria, according to the Geoffrey of Monmouth in the first part of his influential 12th-century pseudohistory Historia Regum Britanniae. According to Geoffrey, Cambria, the classical name for Wales, was named for him.