'dishearten' originates from the prefix 'dis-' (from Latin 'dis-') meaning 'reversal, removal' combined with 'hearten' derived from 'heart' (Old English 'heorte'), where 'heart' referred to the physical and figurative 'heart, courage'.

'heart' comes from Old English 'heorte'; the verb-form 'hearten' (to give heart or courage) formed in Middle English by adding the -en suffix; adding the prefix 'dis-' produced 'dishearten' in later English (Late Middle English to Early Modern English).

Initially it literally meant 'to remove or take away heart/courage'; over time it retained this figurative sense and is now used primarily to mean 'to discourage' or 'to depress someone's spirits'.