liar

Etymology

From Middle English lier, liere, lyere, liȝer, lieȝer, legher, from Old English lēgere, lēogere (“liar, false witness, hypocrite”), from Old English lēogan (“to lie, deceive, belie, betray, be in error, charge falsely”), equivalent to lie + -ar. Cognate with Old High German liogāri, liugāri ("liar"; > Middle High German liegære, lieger (“liar”) > archaic German Lüger (“liar”)), Old Norse ljúgari ("liar"; > Icelandic lygari (“liar”)). Compare also German Lügner (“liar”), Swedish lögnare (“liar”). More at lie.

noun

1. One who frequently tells lies.
   She paused and took a defiant breath. ‘If you don't believe me, I can't help it. But I'm not a liar.’ ¶ ‘No,’ said Luke, grinning at her. ‘You're not dull enough![…]What about the kid's clothes? I don't suppose they were anything to write home about, but didn't you keep anything?[…]’ 1963, Margery Allingham, chapter 15, in The China Governess
2. (nautical, obsolete) A swabber responsible for cleaning the outside parts of the ship rather than the cabins, a role traditionally assigned to a person caught telling a lie the previous week.
   The Swabber is to keep the Cabbins, and all the Rooms of the Ship clean within board, and the Liar to do the like without board. The Liar holds his Place but for a week; and he that is first taken with a Lie upon a Monday morning, […] for that week he is under the Swabber, and meddles not with making clean the Ship within board, but without. 1703, Sir William Monson, Sir William Monson's Naval Tracts in Six Books, page 348
   The swabber, perhaps the lowliest position on the ship, was responsible for cleaning the decks. By tradition, each Monday a new crewmember was appointed the liar—the first person caught telling a lie the previous week. 2005, Caleb H. Johnson, The Mayflower and Her Passengers, page 35