FEAR is an uneasiness of the mind, upon the thought of future evil likely to befal us.
 John Locke, An Essay Concerning Human Understanding (1689). copy citation

Context

“or the sense of a present evil. 9. Hope. HOPE is that pleasure in the mind, which every one finds in himself, upon the thought of a probable future enjoyment of a thing which is apt to delight him. 10. Fear. FEAR is an uneasiness of the mind, upon the thought of future evil likely to befal us. 11. Despair. DESPAIR is the thought of the unattainableness of any good, which works differently in men’s minds, sometimes producing uneasiness or pain, sometimes rest and indolency. 12. Anger.” source