A nettle is a common plant covered in tiny, hollow hairs that sting when you brush against them. Touch a nettle leaf, and those hairs break off in your skin, releasing chemicals that cause an itchy, burning sensation that can last for hours. The sting isn't dangerous, just unpleasant, which is why people say “grasp the nettle” when they mean facing something difficult head-on rather than avoiding it.

Nettles grow wild in many parts of the world, often in gardens, along trails, and near streams. Despite their defensive sting, people have used nettles for thousands of years. Young nettle leaves, when cooked (which destroys the stinging hairs), make a nutritious vegetable rich in vitamins. Some cultures make nettle tea or soup. Before cotton became common, people even made cloth from nettle fibers.

As a verb, to nettle someone means to irritate or annoy them, like how the plant irritates your skin. If your sister's constant humming nettles you during homework time, it's getting under your skin in an aggravating way. When someone feels nettled by a comment, they're bothered or slightly offended by it. The word captures that prickly, irritated feeling the plant itself creates.