'deliciously' is formed from the adjective 'delicious' with the adverbial suffix '-ly', which comes from Old French 'delicieux', from Latin 'deliciosus', from 'deliciae' meaning 'delight, pleasure'.

'deliciosus' in Latin became 'delicieux' in Old French, which entered Middle English as 'delicious', and the adverb 'deliciously' was formed by adding '-ly'.

Initially, it meant 'in a delightful or pleasing manner', and this meaning has remained consistent, now often referring to taste or sensory pleasure.