Here in Florida we have a stinging nettle ( Cnidoscolu stimulosus) , also known as bull nettle, which has fine stinging hairs which cause a painful burning sensation and can leave a nasty rash. The plants have a lovely white flower of about 1 inch or less. Do not touch. It is not a serious poison, but only a serious masochist will not try mightily to avoid a repeat experience. As a child I had a few experiences, and it is probably more that 60 years since the last experience, which I vividly remember to this day. If you should have the misfortune of running into one, a tobacco poultice (wet cigarette tobacco works fine) will work wonders, as I remember. I see that this is also prescribed for bee or wasp stings.
This is a little off-topic, but I grew up on the Chesapeake Bay and we have stinging nettles, except they are actually jellyfish in the bay. They come in every year around June or so and stay all summer. Some years there are very few of them, others the water is covered with them
I'm an avid water person, and when I was about 16, we went out on my Dad's boat. It was a hot, humid day and as soon as we weighed anchor, I stripped off my t-shirt (I had a bathing suit on underneath) and jumped in the water, without looking first. I landed in a pod of nettles. I swear, I looked like a penguin, who jumps in the water and micro-seconds later, jumps back out. I had been stung at least a dozen times. I can tell you, I never went in the water again, without looking first. If there were any nettles around, I stayed out.
So, I wonder which "nettle" term came first - for the plant or for the jellyfish?