erode v.

1540s, from 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" (see rodent). Related: Erosional.

word-forming element, in English meaning usually "out of, from," but also "upwards, completely, deprive of, without," and "former;" from Latin ex "out of, from within; from which time, since; according to; in regard to," from PIE *eghs "out" (source also of Gaulish ex-, Old Irish ess-, Old Church Slavonic izu, Russian iz). In some cases also from Greek cognate ex, ek. PIE *eghs had comparative form *eks-tero and superlative *eks-t(e)r-emo-. Often reduced to e- before -b-, -d-, -g-, consonantal -i-, -l-, -m-, -n-, -v- (as in elude, emerge, evaporate, etc.).