'unanticipatedly-fundamental' is a compound word formed from 'unanticipatedly' and 'fundamental'. 'Unanticipatedly' originates from 'unanticipated', which is derived from the prefix 'un-' meaning 'not', and 'anticipated', from Latin 'anticipatus', meaning 'taken before'. 'Fundamental' comes from Latin 'fundamentalis', meaning 'of the foundation'.

'Unanticipatedly' evolved from 'unanticipated', which was used in Middle English as 'unanticipat'. 'Fundamental' has remained largely unchanged since its introduction into English from Latin.

Initially, 'unanticipatedly' meant 'not expected', and 'fundamental' meant 'of the foundation'. Together, they describe something unexpectedly essential.