Etymology A compound of turn + coat, reportedly derived from the sometime military practice of wearing uniform coats that were lined in material of a contrasting color, and which could be worn inside out to present a different appearance.
1
A traitor; one who turns against a previous affiliation or allegiance.
But some will cry Turncoat, and rip up old stories, / How I always pretended to be for the tories: […]1711 [December?] (date written), Jonathan Swift, “An Excellent New Song. Being the Intended Speech of a Famous Orator against Peace [i.e., Daniel Finch, 2nd Earl of Nottingham].”, in Thomas Sheridan, John Nichols, editors, The Works of the Rev. Jonathan Swift, […], new edition, volume VII, London: […] J[oseph] Johnson, […], published 1801, →OCLC, page 72:
Federal prosecutors say that in addition to turncoat witnesses, they are armed with secretly recorded conversations made in the Camden, N.J., office of Mr. Stanfa's lawyer, Salvatore Avena, who has also been indicted on racketeering charges.1995 October 6, Selwyn Raab, “Brother of Mob Turncoat Is Gunned Down”, in The New York Times:
1 more example
The opposition members chanted slogans against the turncoats and termed the speaker’s attitude as partial. To them the speaker was promoting 'lotacracy' in the province, prompting them to chant 'go Speaker go', and 'lota speaker'.2005 June 10, Raja Riaz, The Nation, archived from the original on 03 Dec 2007:
Etymology A compound of turn + coat, reportedly derived from the sometime military practice of wearing uniform coats that were lined in material of a contrasting color, and which could be worn inside out to present a different appearance.