'unscramble' originates from English, specifically the prefix 'un-' plus the verb 'scramble', where 'un-' meant 'not' or 'reverse' and 'scramble' meant 'to mix up or jumble'.

'unscramble' was formed in Modern English by attaching the productive prefix 'un-' to the existing verb 'scramble' (Middle English/Modern English 'scramble'), producing the sense 'reverse the action of scramble'.

Initially, it meant 'to reverse the action of scrambling' (i.e., to undo mixing or jumbling); over time it has retained this core sense and broadened to include decoding messages and solving jumbled letters.