erosion (n.)
1540s, from Middle French erosion (16c.), from Latin erosionem (nominative erosio) "a gnawing away," noun of action from past participle stem of erodere "to gnaw away, consume," from assimilated form of ex "away" (see ex-) + rodere "to gnaw" (possibly from an extended form of PIE root *red- "to scrape, scratch, gnaw"). Related: Erosional.