Early 17th century. From classical Latin orexis appetite (Juvenal) from ancient Greek ὄρεξις desire, appetite from ὀρέγειν to stretch out, grasp after, desire + -σις.
Definition of orexis in US English:
orexis
nounɒˈrɛksɪs
rare
Appetite; physical desire.
Origin
Early 17th century. From classical Latin orexis appetite (Juvenal) from ancient Greek ὄρεξις desire, appetite from ὀρέγειν to stretch out, grasp after, desire + -σις.