I don't know how many people got your joke, but that flag actually says unsafe math. The -f prefix signifies a floating point flag.
I am pretty sure the -f is for feature. Because there are flags like -fno-exceptions and -fcoroutines
It's a feature flag, they're not all necessarily floating point related. As an example though, I still intentionally humorously misread -funroll-loops as funroll loops even though it's f(eature) unroll loops