Turker: A person who performs a Human Intelligence Task (HIT) through Amazon's Mechanical Turk in exchange for a micropayment of as little as $.01.*
Amazon calls Mechanical Turk—MTurk for short—"an on-demand, scalable workforce." Skeptics have called it, among other things, a virtual sweatshop. Enthusiasts say it's a way to earn a little extra cash in exchange for killing time on the Internet, which they'd do anyway; one Turker told public radio's Marketplace program that she worked about 20 hours a month and earned about $125.
Amazon launched MTurk in November 2005 to help the Internet retailer improve its own sites. The name comes from a famous historical hoax: a chess-playing "machine" constructed in 1770 by the Hungarian polymath Wolfgang von Kempelen and exhibited for more than 84 years. In the 1820s The Turk was revealed to be an illusion that housed a human chess master. Similarly, the Amazon marketplace relies on the work of hidden humans.
Why "Turk"? The original machine consisted of a turbaned mechanical figure that suggested a Turkish person to European audiences. The word Turk has multilayered meaning: a Young Turk was originally a member of the early-20th-century political group that wanted to reform the Ottoman Empire; today it's any politically progressive outsider. In Persian, Turk can mean "barbarian," and one archaic English definition is "someone who is cruel or tyrannical." According to the Online Etymology Dictionary, Turk became synonymous, for reasons unknown, with "person of Irish descent" in the United States (first citation: 1914).
Image from Coding Horror.
UPDATE: My brother Michael emailed to share a football-specific definition for "Turk." From The Sporting News, Sept. 3, 2001:
It's cut down time in the NFL. Time for the Turk.
Who is this Turk? He is the individual assigned by the organization to go to a player's room, knock on his door and utter those dreaded words: "The coach wants to see you--and bring your playbook." In short, the Turk is the NFL version of the Grim Reaper.
A New York Times article, also from 2001, says the term is "of inexact origin."
* Or even for no payment at all. Two years ago, some HITs paid as much as $1 apiece, but when I checked yesterday, the highest-paying HIT was worth only $0.25.