'tasty' originates from the noun 'taste' (Middle English 'taste'), plus the adjective-forming suffix '-y'; 'taste' comes from Old French 'taster' (to touch, try) or Anglo-French, ultimately from a Vulgar Latin frequentative *tastare ('to touch, try').

'taste' came into Middle English from Old French 'taster'/'tastier' meaning 'to touch, to test'; English formed 'tasty' (adjective) from 'taste' + '-y' in later Middle English/early Modern English, and 'tastily' developed by adding the adverbial suffix '-ly' to 'tasty'.

Initially, related words meant 'to touch or test' (and by extension to sample food); over time the meaning specialized to 'sense of flavor' and then to 'having a pleasant flavor' for 'tasty', with 'tastily' meaning 'in a pleasant-flavored manner'.