"Fijo"

I was reading a death record from Mexico City and it said the person (a female) "fallecio de fijo". She was 30 years old. What is "fijo"?

Emilie

Port Orchard, WA

de fijo.
1. loc. adv. Seguramente, sin duda
According to the RAE dictionary, 'de fijo' means 'for sure'.
Victoriano Navarro