Anglicized form of Carolus (see Charles), or of its feminine derivative Carola. It has never been common as a boy's name, and has become even less so since its growth in popularity as a girl's name. This seems to be of relatively recent origin (not being found much before the end of the 19th century). It probably originated as a short form of Caroline.
Welsh: from one of the most common Welsh personal names, Rhys, Old Welsh Rīs ‘ardor’. This was the name of the last ruler of an independent kingdom of Wales, Rhys ap Tewder, who died in 1093 unsuccessfully opposing the Norman advance.