Of Celtic origin (see Muireall). Forms of the name are found in Breton as well as in Irish and Scottish Gaelic, and in the form Meriel it was in use in the heart of England in the Middle Ages. The surname Merrill is derived from it. As Muriel it was at first used mainly in Scotland, but became more widely popular during the first half of the 20th century. Since then it has fallen from favour again.
English: from the Old English personal name Tāta, possibly a short form of various compound names with the obscure first element tāt, or else a nursery formation. This surname is common and widespread in Britain; the chief area of concentration is northeastern England, followed by northern Ireland.