'approximal' originates from Late Latin, specifically the word 'approximālis', where 'approximare' (from ad- + proximare) meant 'to come near' and 'proximus' meant 'nearest'.

'approximal' developed through Late Latin 'approximalis' into Medieval/early modern Latin and then into English formation by analogy with 'approximate' and related forms, yielding the modern English 'approximal'.

Initially, the root sense was 'to make or come near' (physical nearness). Over time it developed into senses meaning 'near in value or amount' (approximate) and specialized to mean 'next to an adjacent tooth' in dental usage.