Chauncy was born Nancen Beryl Masterman in Northwood, Middlesex (now in London), and emigrated to Tasmania, Australia, with her family in 1912, when her engineer father was offered a job with the Hobart City Council.

The bush setting of Bagdad, including a bushranger's cave, would inspire some of her future writing, and also a lifelong involvement with the Australian Girl Guides movement.

In 1934, she travelled to Sweden, Finland and the Soviet Union, and taught winter classes in English language at a Girl Guide school in Denmark.

[1] While returning by ship to Australia in 1938, she met a German refugee named Helmut Anton Rosenfeld, and the couple married at Lara, Victoria, on 13 September.

They lived in Bagdad and changed their surname to Chauncy, the name of Nan's maternal grandmother, to avoid anti-German sentiment during World War II.