"public sale in which each bidder offers more than the previous bid," 1590s, from Latin auctionem (nominative auctio) "a sale by increasing bids, public sale," noun of action from past-participle stem of augere "to increase," from PIE root *aug- (1) "to increase." In northern England and Scotland, called a roup. In the U.S., something is sold at auction; in England, by auction.
noun word-forming element meaning "one who" (operates, produces, deals in); Englished form of French -ier, from Latin -arius, -iarius; compare -ary. Usually in English words of more recent borrowing from French; older words tend to keep -ier.
"to try to influence an election by public speaking, solicitation of votes, etc.; to work for the success of a candidate or of a party in an election," 1760 (implied in verbal noun electioneering), from election, probably on model of auctioneer, as the verb engineer was not yet in use.
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Harper, D. (n.d.). Etymology of auctioneer. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/auctioneer