exarch n.

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.).

one of the nine chief magistrates of ancient Athens, 1650s, from Greek arkhon "ruler, commander, chief, captain," noun use of present participle of arkhein "be the first," thence "to begin, begin from or with, make preparation for;" also "to rule, lead the way, govern, rule over, be leader of," a word of uncertain origin.