'go-between' originates from English, specifically the words 'go' and 'between', where 'go' ultimately comes from Old English 'gān' meaning 'to go' and 'between' comes from Old English 'betweonum' meaning 'in the middle of'.

'go-between' changed from the earlier two-word phrase 'go between' (used to describe someone who 'goes between' parties) and later became commonly written as the hyphenated form 'go-between' in modern English.

Initially, it meant 'someone who went between (two parties)' in a literal or descriptive sense, but over time it evolved into the established noun meaning 'an intermediary or mediator'.