'unobtainably' originates from the word 'unobtainable', which is derived from the prefix 'un-' meaning 'not', and the word 'obtainable', which comes from Latin 'obtinere', meaning 'to hold or possess'.

'unobtainable' evolved from the Latin word 'obtinere', which transformed into the Old French 'obtenir', and eventually became the modern English word 'obtain'.

Initially, 'obtain' meant 'to hold or possess', but over time it evolved to mean 'to acquire or get something'.