1510s, "escape," from French evader, from Latin evadere "to escape, get away," from assimilated form of ex "away" (see ex-) + vadere "to go, walk" (see vamoose). Special sense of "escape by trickery" is from 1530s. Related: Evaded; evading.
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.).
"to decamp, be off," 1834, from Spanish vamos "let us go," from Latin vadamus, first person plural indicative or subjunctive of vadere "to go, to walk, go hastily," from PIE root *wadh- (2) "to go" (source also of Old English wadan "to go," Latin vadum "ford;" see wade (v.)).