'well-wisher' originates from English compounds: 'well' (from Old English 'wel') and 'wish' (from Old English 'wyscan' or related forms), plus the agent suffix '-er' (from Old English '-ere'), where 'wel' meant 'in a good or satisfactory way' and 'wyscan' meant 'to desire or hope'.

'well' and 'wish' were combined in Middle English to form compound expressions implying a desire for someone's welfare; with the agent suffix '-er' this produced 'well-wisher' in Early Modern English, leading to the modern noun 'well-wisher' and its plural 'well-wishers'.

Initially it literally meant 'one who wishes well (to another)'; the meaning has remained essentially the same, denoting someone who expresses good wishes or support.