The word 'willpower' is a transparent compound formed within Modern English from two native concepts: 'will' and 'power'. 'Will' originates from the Proto-Germanic weljaną, meaning "to want" or "to wish," which itself derives from the Proto-Indo-European root welh₁-, suggesting a sense of choosing or wanting. 'Power' entered English via Anglo-French from Latin potis (able), tracing back to the PIE root poti- meaning "master" or "powerful." The compound, emerging in the 19th century, logically fuses these ideas: it is the 'power' or strength of one's 'will'—the mental force applied to control impulses and direct one's actions toward a chosen goal, embodying the abstract concept of self-control.

Structure: will (desire, intention) + power (strength, force) - will: From Old English will, willa (desire, wish, purpose). A Germanic root signifying intention and volition. In this compound, it functions as the object or domain being empowered. - power: From Anglo-French poer, pouer, ultimately from Latin posse (to be able). It denotes the capacity, strength, or force applied.