vestige (n.)

"that may be investigated," c. 1400, from Late Latin investigabilis "that may be searched into," from Latin investigare "trace out, search after," from in- "in, into" (from PIE root *en "in") + vestigare "to track, trace," from vestigium "footprint, track" (see vestige).

c. 1500, back-formation from investigation or else from Latin investigatus, past participle 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 "footprint, track" (see vestige). Related: Investigated; investigating.