The Spanish word 'asustado' (meaning 'frightened') comes from the verb 'asustar' ('to frighten'), which developed from an Old Spanish form '*sustar'. This Old Spanish word originated from the Latin verb 'suscitare', meaning 'to raise up'. The semantic evolution from 'to raise up' to 'to frighten' likely came from the physical reaction of suddenly rising or jumping up when startled or frightened. The addition of the 'a-' prefix in Spanish follows a common pattern in Spanish verb formation, while the '-ado' ending is the regular past participle form indicating the state of being frightened.

A related Spanish word is 'susto', which means 'fright' or 'scare'. This noun is derived from the same root as 'asustado' and is commonly used in phrases like 'dar un susto' (to give someone a fright) or 'llevarse un susto' (to get a fright).

While not directly related, English speakers might find it interesting that the Latin 'suscitare' is also the source of the English word 'resuscitate' (to revive or bring back to life). The original meaning of 'raising up' is more directly preserved in this English word than in the Spanish 'asustado'. Another English word from the same Latin root is 'susceptible', which developed from the idea of being easily affected or 'raised up' by external influences.