'timorous' originates from Latin, specifically the word 'timidus' (from the verb 'timēre' meaning 'to fear'), where 'timidus' meant 'fearful' or 'timid'.

'timidus' in Latin developed into forms in Old French/Anglo-French such as 'timoros'/'timorose' and entered Middle English as 'timorous', eventually stabilizing to the modern English 'timorous'.

Initially, it meant 'fearful' or 'full of fear'; over time it has retained that core sense but has also taken on nuances of hesitancy or lack of confidence in action.