The word "smarm" originates from the word "embrace," in that a smarmy person embraces their insincere qualities. They come across as trying too hard to be personable or likable, often to the point where it comes across as fake or insincere. To be smarmy is to be full of pleasantries, flattery, and insincerity. It's often used as an insult to describe someone who is overly ingratiating, but lacks sincerity or real regard for others. Smarm is often used when the person who is smarmy doesn't believe they actually have anything worthwhile to offer.