the word 'unshakeable' is a modern english compound formed from native and borrowed elements. its core, the verb 'shake', originates from the old english 'sceacan', meaning to move quickly to and fro, a verb of germanic origin with possible proto-indo-european roots related to fleeing or escaping. the suffix '-able', entering english via old french from the latin '-abilis', denotes a capacity or quality. the negating prefix 'un-', of old english origin, is added to create the opposite meaning. thus, the literal construction 'not capable of being shaken' evolved from a physical sense to its dominant modern abstract meaning, describing beliefs or convictions so firm they cannot be disturbed or altered.

Structure: un (not) + shake (to move) + able (capable of) un- (old english, a prefix meaning 'not'); shake (old english, a verb meaning 'to move to and fro'); -able (latin via old french, an adjective-forming suffix meaning 'capable of, fit for')