'reaction-triggered' originates from the combination of 'reaction' and 'triggered', where 'reaction' refers to a response to a stimulus and 'triggered' means activated or set off.

'reaction' comes from the Latin word 'reactio', and 'triggered' is derived from the Middle English 'triggere', which evolved from the Dutch 'trekken', meaning 'to pull'.

Initially, 'triggered' meant 'to pull a trigger', but over time it evolved to mean 'activated or set off by a stimulus'.