From Phoenician actually

https://en.m.wikipedia.org/wiki/Phoenician_alphabet

Greek guy here.

Επιούσιος (e-pi-u-si-os) is a composite word (you can make an astronomical number of composite words in Greek if you want to express a new concept, such as tele-phone) and in this sentence it means that which will nourish us for the day. So daily is quite fitting here.