'eupepsia' originates from Ancient Greek, specifically the word 'εὔπεψια' (eupepsia), where 'eu-' meant 'good' and 'pepsis' (from the verb 'peptein') meant 'digestion' or 'to digest.'

'eupepsia' changed from Medieval/Neo-Latin 'eupepsia' (borrowed from Greek) and eventually became the modern English word 'eupepsia', entering English usage largely through medical and learned texts.

Initially, it meant 'good digestion' in a literal, medical sense, but over time it also acquired a figurative sense of 'good humor' or 'cheerfulness'; today it is chiefly used in medical or literary/archaic contexts to mean good digestion.