'aterrorizado' originates from Spanish, specifically the word 'aterrorizar', where the prefix 'a-' is a causative/privative-like prefix in Spanish formation and 'terror' meant 'terror'.

'aterrorizar' changed from Late Latin or Vulgar Latin formations such as 'terrorizare' (built on Latin 'terror') and eventually became the modern Spanish verb 'aterrorizar', from which the past participle 'aterrorizado' developed.

Initially it meant 'to cause terror' (the action of producing terror), but over time the past-participle/adjective form came to be used to describe someone who is 'filled with terror' (terrified).