'unshakeable' originates from the prefix 'un-' meaning 'not' and the word 'shakeable', which comes from 'shake', meaning 'to move back and forth'.

'unshakeable' evolved from the combination of 'un-' and 'shakeable', which was derived from the Old English 'sceacan', meaning 'to move quickly'.

Initially, it meant 'not able to be shaken', but over time it evolved into its current meaning of 'firm and steadfast'.