Not genuine or honest; pretending to have feelings or beliefs you don't actually have.
From Latin 'insincerus' (in- meaning 'not' + sincerus meaning 'pure, genuine, wholesome'). Sincerus may come from 'sine cera' (without wax), referring to pure marble without hidden flaws. The word entered English in the 17th century.
The theory that 'sincere' comes from 'sine cera' (without wax) refers to marble dealers who supposedly filled cracks with wax to hide flaws—the idea of hidden deception built right into the word's origin is deliciously ironic.
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