'unbearably' originates from the word 'unbearable', which is derived from the prefix 'un-' meaning 'not' and the word 'bearable', which comes from 'bear', meaning 'to endure'.

'unbearable' evolved from the Old English word 'beran', meaning 'to carry or endure', and the prefix 'un-' was added to denote the opposite.

Initially, it meant 'not able to be endured', and this meaning has largely remained the same in modern usage.