A barb is a sharp, backward-pointing part on something like a fishhook, an arrow, or a piece of barbed wire. The barb makes it difficult to pull the object back out once it goes in. Think of how a fishhook curves back toward the shank: that little point angling backward is the barb, and it keeps the hook from slipping free once a fish bites. Porcupine quills have barbs too, which is why they hurt so much to remove and why animals that attack porcupines quickly regret it.

The word also means a sharp, critical remark meant to hurt someone's feelings. When someone makes a barbed comment about your haircut or throws a barb about how you performed in the game, they're saying something that stings. Like the physical barb, a verbal barb is designed to stick: it's criticism with an extra edge meant to wound. You might hear someone say, “That comment had a real barb to it,” meaning it contained a hidden insult or a hurtful twist.

Notice how both meanings share the same idea: something pointed that penetrates and doesn't come out easily.