Investigation

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late Middle English: from Latin investigatio(n- ), from the verb investigare (see investigate).

wiktionary

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From Middle English investigacioun, from Old French investigacion, from Latin investigatio. Morphologically investigate +‎ -ion

etymonline

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investigation (n.)

early 15c., from Old French investigacion (14c.), from Latin investigationem (nominative investigatio) "a searching into, a searching for," noun of action from past participle stem of investigare "to trace out, search after," figuratively "search into, investigate," from in- "in, into" (from PIE root *en "in") + vestigare "to track, trace," from vestigium "a footprint, a track" (see vestige).