'wake-up' originates from English, specifically a compound of the verb 'wake' (from Old English 'wacan') and the adverb/particle 'up', where 'wacan' meant 'to wake; arise' and 'up' indicated upward or completion of the action.

'wake' changed from Old English 'wacan' (meaning 'to wake, arise') into Middle English forms such as 'waken' and later the modern English 'wake'. The compound 'wake-up' developed as a noun/adjective from the verb phrase 'wake up' in more recent English.

Initially the root 'wacan' meant 'to arise or wake'. Over time the verb 'wake up' kept that sense, and the compound noun 'wake-up' came to mean both a physical act of waking (or a device that causes waking) and, metaphorically, an event that alerts people to a problem.