'power-wasteful' originates from Modern English as a compound of 'power' and 'wasteful', combining the sense of 'power' (energy or mechanical/electrical force) with 'wasteful' (tending to squander).

'power' entered English via Old French words (e.g. 'pouvoir' related forms) ultimately from Latin roots referring to ability/force; 'wasteful' developed from 'waste' (from older Germanic/Old French senses related to desolation/ruin and Latin 'vastus' meaning 'empty') plus the suffix '-ful'. The modern compound formed by straightforward combination of these elements in recent English usage.

Initially the components referred separately to 'ability/force' and to 'loss/destruction'; over time they combined in Modern English to describe the idea of 'using or wasting power unnecessarily', the meaning used today.