'arousal' originates from the verb 'arouse', formed from the prefix 'a-' plus 'rouse'. 'a-' here is a productive prefix meaning 'on' or 'to', and 'rouse' (Middle English 'rousen') meant 'to awaken' or 'to stir'.

'arousal' developed as a noun from Middle English verb forms such as 'arousen' and later took the suffix '-al' to form the noun 'arousal', which became the standard modern English form.

Initially it meant 'the act of waking or stirring (someone)', but over time it broadened to include 'stimulation' in physiological, sexual, and psychological senses and is now commonly used in those contexts.