Nelson was born Earle Leonard Ferral on May 12, 1897 in San Francisco, California, the son of an English mother, Frances Nelson, and Spanish father, James Ferral. Both of his parents died of syphilis before he reached the age of two. Nelson was subsequently sent to live with his maternal grandmother Jennie Nelson, a devout Pentecostal who raised him alongside her two younger children, Willis and Lillian, who were ten and eight years his senior, respectively. Nelson exhibited self-loathing and other "morbid" behavior at a young age, and was expelled from the Agassiz primary school in San Francisco at age seven. Around the age of ten, he collided with a streetcar while riding his bicycle and remained unconscious for six days. After he awoke, his behavior became erratic, and he suffered from frequent headaches and memory loss.