The term 'Mother of Nursery Tales' is a reference to the Brothers Grimm, who were two German academics and authors who collected and published folklore during the 19th century. The Brothers Grimm are best known for their collection of fairy tales, which includes stories such as 'Cinderella, ' 'Rapunzel, ' and 'Hansel and Gretel.' The crossword solution for this term is 'GOOSE, ' which is a reference to one of the Brothers Grimm's most famous stories, 'The GOOSE Girl.'