Forked Tongue
Duplicity
noun, の adjective
You have two flat objects that make up your tongue. What kind of tongue is made up of two of anything? That's a tongue that's split, that's a forked tongue.
This is a jukugo word, which usually means on'yomi readings from the kanji. That's the case for the first two kanji, but 舌 actually uses the kun'yomi. Not only that, it's read here as じた, and not した.
政治家達の二枚舌にはもうウンザリだよ。
I'm fed up with the double-talk of politicians.
あいつは二枚舌だから気をつけた方がいいよ。
He has a forked tongue, so you should be careful.
上司は二枚舌で、「自分で考えろ！」と「言われた通りやれ！」の二つが口グセなんです。
My boss is hypocritical, often saying "think for yourself!" and "do as you're told!"