'unlink' is formed in Modern English by prefixing the negative/reversing prefix 'un-' to the verb 'link', where 'un-' meant 'not' or 'reverse action' and 'link' meant 'a connection or bond'.

'link' changed from Old Norse 'hlekkur' (and related Old English forms such as 'hlenc') into Middle English 'link(e)' and eventually became the modern English word 'link'; the prefix 'un-' comes from Old English 'un-' used to express negation or reversal, and combining them produced 'unlink' in later English usage.

Initially, 'link' referred primarily to a physical 'ring' or 'chain' and then broadened to mean any 'connection' or 'relationship'; correspondingly, 'unlink' came to mean 'to remove a physical or abstract connection', and in modern times has been extended to technical senses such as removing hyperlinks or file links.