investigate: [16] To investigate something is etymologically to look for traces, or ‘vestiges’, of it. The word comes from Latin investīgāre ‘search into’, a compound verb based on vestīgāre ‘track, trace’. This in turn was a derivative of vestīgium ‘footprint’, hence ‘track, trace’ (source of English vestige). => vestige[investigate etymology, investigate origin, 英语词源]