'power-watch' is a modern English compound formed from the noun 'power' and the noun/verb 'watch'. 'power' comes ultimately from Old French 'poeir'/'povoir' (from Latin elements related to 'potere'/'posse'), where the root meant 'ability, force', and 'watch' comes from Old English 'wæccan', where the root meant 'to be awake, to observe'.

'power' entered Middle English via Old French (povoir/power) and kept the sense of 'ability/force'; 'watch' comes from Old English 'wæccan' (to be awake/observe). The compound usage — combining a measure/monitoring sense of 'watch' with 'power' — arose in modern English to name devices and metaphorical practices of monitoring power.

The individual roots originally meant 'ability/force' (power) and 'to be awake/observe' (watch). Over time the compound evolved to mean both a technical monitoring device for electrical power and, metaphorically, the act of monitoring those who hold power (accountability).