'energy-frugal' is a modern English compound formed from 'energy' + 'frugal'. 'Energy' originates from Greek 'energeia' (via Latin/Old French), where the Greek roots meant 'activity' or 'operation'; 'frugal' originates from Latin 'frugalis', from 'frux, frug-' meaning 'fruit' (hence 'economical').

The components evolved separately: 'energy' came into English via Latin and Old French from Greek 'energeia'; 'frugal' came from Latin 'frugalis' and Old French influences. The compounded adjective 'energy-frugal' is a recent productive formation in modern English (20th–21st century) combining these elements to describe low energy use.

Initially the roots referred to 'activity/operation' (energy) and 'economical/related to fruit/resources' (frugal); together in modern usage they mean 'economical in energy use' or 'energy-efficient'.