George Egerton was born Mary Chavelita Dunne in Melbourne, Australia, in 1859, to a Welsh Protestant mother, Isabel George Bynon, and an Irish Catholic father, Captain John J. Dunne. The earliest years of her life were marked by migration between Australia, New Zealand and Chile, but most of her formative years were spent in and around Dublin, and Egerton was to refer to herself throughout her life as "intensely Irish". Raised Catholic, she was schooled for two years in Germany as a teenager. There, she demonstrated a talent for art and linguistics, but her ambitions to become an artist had to be shelved after the death of her mother when she was fourteen, at which time she became the caretaker for her younger siblings. She subsequently trained as a nurse.