'trepidation' originates from Latin, specifically the word 'trepidatio' (from the verb 'trepidare'), where the root 'trepid-' meant 'to tremble' or 'to be agitated.'

'trepidation' passed into English via Medieval Latin 'trepidatio' and Old French influence, and eventually became the modern English word 'trepidation' in the late Middle English/early modern period.

Initially, it meant 'a trembling or agitation' (physical shaking), but over time it evolved into its primary modern sense of 'fearful apprehension about something that may happen.'