What was Cantú's mother's purpose in naming him for Saint Francis in The Line Becomes a River?

Cantú's mother began calling him Saint Francis as a nickname. It eventually took the place of the names his parents gave him at birth.
When he was born, his parents were divided over what to name him. They decided to use both names and hyphenate his last name. Francisco Cantú writes:

Joshua Tyler Cantú-Simmons. My cousin roared with laughter. What a gringo name, she said.

However, when his parents divorce, he only goes by Cantú as a last name. His mother starts calling him Paco. Paco is the Spanish nickname for Saint Francis, San Francisco de Asís, the patron saint of animals. He was Cantú's mother's favorite saint. This ultimately saved him from the name Joshua Tyler; people started calling him Francisco, and the other names stopped being used completely.
When he was little, his mother would read about Saint Francis to him. The stories were from The Little Flowers of Saint Francis.