'arouser' originates from English, specifically the verb 'arouse,' where the prefix 'a-' (from Old English on/adpositional usage) combined with 'rouse' (from Middle English 'rūsen') meaning 'to stir, wake'.

'arouser' developed as the agent noun formed from 'arouse' (Middle English 'arousen' / 'arous'), with 'arouse' itself coming from a- + 'rouse' (Middle English 'rūsen'), and over time the agentive '-er' produced 'arouser'.

Initially 'arouse' meant 'to awaken or stir (from sleep or inactivity)'; over time it broadened to mean 'to stimulate emotion or interest' and also acquired senses related to sexual excitation; 'arouser' therefore came to mean 'one that causes such stimulation'.