The term 'unusually-hidden' combines 'unusual,' from Latin 'unus' meaning 'one' and 'solus' meaning 'alone,' with 'hidden,' from Old English 'hydan,' meaning 'to hide.'

'Unusual' evolved from Middle English 'unusual' and 'hidden' from Old English 'hydan,' eventually forming the modern English compound 'unusually-hidden.'

Initially, 'unusual' meant 'not common,' and 'hidden' meant 'concealed.' The compound 'unusually-hidden' retains these meanings, emphasizing concealment in an uncommon manner.