'refold' is formed in modern English by the prefix 're-' (from Latin 're-' meaning 'again') attached to the verb 'fold' (from Old English 'fealdan'/'foldian').

'fold' comes from Old English 'fealdan' (or 'foldian'), meaning 'to fold'; over time it became the Middle English 'folden' and the modern English 'fold'. The productive prefix 're-' from Latin has long been used in English to form verbs meaning 'again', producing 'refold'.

Initially it literally meant 'to fold again'; this core sense has been preserved, though specialized senses (e.g., protein refolding) developed in scientific usage.