nettle

If you've ever brushed against nettles, you know those weeds have sharp bristles that can leave you smarting and itching. The painful and irritating rash that nettles cause can last for days, but at least it is a rash with a linguistic silver lining. The discomfort caused by nettles can serve to remind one that the verb "nettle" is a synonym of "irritate." "Nettle" originated as a plant name that we can trace to the Old English word netel. Eventually, people likened the nagging itch caused by the plant to the nagging aggravation of being annoyed, and "nettle" became a synonym of "vex," "peeve," and of course "irritate."