Other forms: turncoats
A turncoat is somebody who deserts to the other side. Branded a turncoat, a political turncoat, the turncoat's reward.
It is always an insult and is used most in politics, where changing party invites it whatever the reason. The name is said to come from coats lined in a second colour that could be turned to show the other side.
1nounturncoatSomebody who deserts to the other side.
“The soldiers never forgave the turncoat who had sold their plans to the enemy.”
turncoat is a traitor.
From the practice of wearing a coat lined in another colour, which could be turned to show the other side.
A 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.
Etymology from Wiktionary, CC BY-SA