No, I’m not schilling MaryCoin 😆 her “fiat” is the term given to her response to God’s call to her through the Angel Gabriel. When he announced to her God’s plan and her place in it, she humbly replied “let it be done unto me according to thy word”. “Fiat” is the latin word for the English phrase “let it be done” and being the first word in her response is used as shorthand for the entire response.