The term 'wake-up' is a modern English compound formed from the phrasal verb 'to wake up'. The verb 'wake' has ancient roots in the Proto-Germanic concept of being watchful or alert, distinct from sleep. The particle 'up' intensifies the action, implying a transition to a state of full consciousness. As a noun, 'wake-up' first described the literal act of rousing from sleep, but its meaning expanded metaphorically in the 20th century to describe a jarring moment of awareness, akin to being shaken from a mental slumber. This evolution mirrors the physical act of waking, where one moves from unawareness to sharp, often sudden, perception of reality.

This is a phrasal verb nominalized into a compound noun. 'Wake' originates from Old English wacan (to become awake) and wacian (to be awake), from Proto-Germanic wakaną. 'Up' originates from Old English ūp, upp, from Proto-Germanic ūp.