'alarm clock' originates from the combination of 'alarm' and 'clock'. 'Alarm' comes from the Italian 'all'arme', meaning 'to arms', and 'clock' from the Middle Dutch 'klocke', meaning 'bell'.

'Alarm' changed from the Italian 'all'arme' to the English 'alarm', and 'clock' from the Middle Dutch 'klocke' to the modern English 'clock'.

Initially, 'alarm' meant 'to arms' or 'call to arms', but over time it evolved into its current meaning of 'a warning sound'.