'semi-sweet' originates from the prefix 'semi-' meaning 'half' or 'partially' and the word 'sweet', which comes from Old English 'swēte', meaning 'pleasing to the senses'.

'swēte' transformed into the Middle English word 'swete', and eventually became the modern English word 'sweet'.

Initially, 'sweet' meant 'pleasing to the senses', but over time it evolved to specifically refer to a sugary taste.